diff --git a/internal/tlcodegen/qt_struct.qtpl b/internal/tlcodegen/qt_struct.qtpl
index 03f22e6d..f71cf055 100644
--- a/internal/tlcodegen/qt_struct.qtpl
+++ b/internal/tlcodegen/qt_struct.qtpl
@@ -842,7 +842,7 @@ func (item *{%s= goName %}) ReadResultJSONWriteResult(r []byte, w []byte) ([]byt
                     }
                 -%}
 // Set field{%s= maybeS %} {%s= mergedFieldsForComment %} in "{%s= affectedType.wr.tlName.String() %}" by changing fieldMask "{%s= field.originalName %}"
-func (item *{%s= goName %}) SetInReturn{%s= mergedFields %}For{%s= affectedType.wr.goGlobalName %}(value bool) {
+func (item *{%s= goName %}) Set{%s= affectedType.wr.goGlobalName %}{%s= mergedFields %}(value bool) {
     if value {
         item.{%s= field.goName %} |= 1 << {%d= int(bit) %}
     } else {
@@ -914,6 +914,8 @@ if mask{%s= field.goName %} & (1<<{%v= index %}) != 0 {
             {%- elseif (fieldProps & FieldUsedAsSize) != 0 -%}
 {%s= field.t.TypeRandomCode(bytesVersion, directImports, struct_.wr.ins, "item."+field.goName, formatNatArgs(struct_.Fields, field.natArgs), field.recursive) %}
 item.{%s= field.goName %} = rg.LimitValue(item.{%s= field.goName %})
+            {%- elseif fieldProps == FieldIsNat -%}
+{%s= field.t.TypeRandomCode(bytesVersion, directImports, struct_.wr.ins, "item."+field.goName, formatNatArgs(struct_.Fields, field.natArgs), field.recursive) %}
             {%- endif -%}
         {%- else -%}
 {%s= field.t.TypeRandomCode(bytesVersion, directImports, struct_.wr.ins, "item."+field.goName, formatNatArgs(struct_.Fields, field.natArgs), field.recursive) %}
diff --git a/internal/tlcodegen/qt_struct.qtpl.go b/internal/tlcodegen/qt_struct.qtpl.go
index fa42a50e..bc79add8 100644
--- a/internal/tlcodegen/qt_struct.qtpl.go
+++ b/internal/tlcodegen/qt_struct.qtpl.go
@@ -1724,10 +1724,9 @@ func (item *`)
 					qw422016.N().S(`"
 func (item *`)
 					qw422016.N().S(goName)
-					qw422016.N().S(`) SetInReturn`)
-					qw422016.N().S(mergedFields)
-					qw422016.N().S(`For`)
+					qw422016.N().S(`) Set`)
 					qw422016.N().S(affectedType.wr.goGlobalName)
+					qw422016.N().S(mergedFields)
 					qw422016.N().S(`(value bool) {
     if value {
         item.`)
@@ -1897,6 +1896,10 @@ item.`)
 				qw422016.N().S(` = rg.LimitValue(item.`)
 				qw422016.N().S(field.goName)
 				qw422016.N().S(`)
+`)
+			} else if fieldProps == FieldIsNat {
+				qw422016.N().S(field.t.TypeRandomCode(bytesVersion, directImports, struct_.wr.ins, "item."+field.goName, formatNatArgs(struct_.Fields, field.natArgs), field.recursive))
+				qw422016.N().S(`
 `)
 			}
 		} else {
diff --git a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestAllPossibleFieldConfigsContainer/cases.testAllPossibleFieldConfigsContainer.go b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestAllPossibleFieldConfigsContainer/cases.testAllPossibleFieldConfigsContainer.go
index 6de638bd..8f228529 100644
--- a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestAllPossibleFieldConfigsContainer/cases.testAllPossibleFieldConfigsContainer.go
+++ b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestAllPossibleFieldConfigsContainer/cases.testAllPossibleFieldConfigsContainer.go
@@ -34,6 +34,7 @@ func (item *CasesTestAllPossibleFieldConfigsContainer) Reset() {
 func (item *CasesTestAllPossibleFieldConfigsContainer) FillRandom(rg *basictl.RandGenerator) {
 	var maskOuter uint32
 	maskOuter = basictl.RandomUint(rg)
+	maskOuter = rg.LimitValue(maskOuter)
 	item.Outer = 0
 	if maskOuter&(1<<0) != 0 {
 		item.Outer |= (1 << 0)
diff --git a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs/cases.testInplaceStructArgs.go b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs/cases.testInplaceStructArgs.go
index 5d4c7454..07b1e49d 100644
--- a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs/cases.testInplaceStructArgs.go
+++ b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs/cases.testInplaceStructArgs.go
@@ -34,6 +34,11 @@ func (item *CasesTestInplaceStructArgs) Reset() {
 }
 
 func (item *CasesTestInplaceStructArgs) FillRandom(rg *basictl.RandGenerator) {
+	item.A1 = basictl.RandomUint(rg)
+	item.A1 = rg.LimitValue(item.A1)
+	item.A2 = basictl.RandomUint(rg)
+	item.A2 = rg.LimitValue(item.A2)
+	item.A3 = basictl.RandomUint(rg)
 	item.Arg.FillRandom(rg, item.A1, item.A2, item.A3)
 }
 
diff --git a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs2/cases.testInplaceStructArgs2.go b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs2/cases.testInplaceStructArgs2.go
index e66ec04d..be075583 100644
--- a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs2/cases.testInplaceStructArgs2.go
+++ b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestInplaceStructArgs2/cases.testInplaceStructArgs2.go
@@ -34,6 +34,12 @@ func (item *CasesTestInplaceStructArgs2) Reset() {
 }
 
 func (item *CasesTestInplaceStructArgs2) FillRandom(rg *basictl.RandGenerator) {
+	item.A1 = basictl.RandomUint(rg)
+	item.A1 = rg.LimitValue(item.A1)
+	item.A2 = basictl.RandomUint(rg)
+	item.A2 = rg.LimitValue(item.A2)
+	item.A3 = basictl.RandomUint(rg)
+	item.A3 = rg.LimitValue(item.A3)
 	item.Arg.FillRandom(rg, item.A1, item.A2, item.A3, item.A3, item.A2)
 }
 
diff --git a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMask/cases.testOutFieldMask.go b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMask/cases.testOutFieldMask.go
index 20f67603..b0c9f8cc 100644
--- a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMask/cases.testOutFieldMask.go
+++ b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMask/cases.testOutFieldMask.go
@@ -57,6 +57,7 @@ func (item *CasesTestOutFieldMask) Reset() {
 
 func (item *CasesTestOutFieldMask) FillRandom(rg *basictl.RandGenerator, nat_f uint32) {
 	if nat_f&(1<<0) != 0 {
+		item.F1 = basictl.RandomUint(rg)
 	} else {
 		item.F1 = 0
 	}
diff --git a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMaskContainer/cases.testOutFieldMaskContainer.go b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMaskContainer/cases.testOutFieldMaskContainer.go
index f6f272ba..59da07c9 100644
--- a/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMaskContainer/cases.testOutFieldMaskContainer.go
+++ b/internal/tlcodegen/test/gen/cases/internal/tlcases/tlCasesTestOutFieldMaskContainer/cases.testOutFieldMaskContainer.go
@@ -32,6 +32,7 @@ func (item *CasesTestOutFieldMaskContainer) Reset() {
 func (item *CasesTestOutFieldMaskContainer) FillRandom(rg *basictl.RandGenerator) {
 	var maskF uint32
 	maskF = basictl.RandomUint(rg)
+	maskF = rg.LimitValue(maskF)
 	item.F = 0
 	if maskF&(1<<0) != 0 {
 		item.F |= (1 << 0)
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc2.myCycle.go b/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc2.myCycle.go
index 9e6ed3cb..2197bba6 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc2.myCycle.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc2.myCycle.go
@@ -32,6 +32,7 @@ func (item *Cyc2MyCycle) Reset() {
 }
 
 func (item *Cyc2MyCycle) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	item.A.FillRandom(rg)
 	item.B.FillRandom(rg)
 }
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc3.myCycle.go b/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc3.myCycle.go
index f848d7d8..cc00093d 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc3.myCycle.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/cycle_e10cb78db8a2766007111b86ce9e11d9/cyc3.myCycle.go
@@ -29,6 +29,7 @@ func (item *Cyc3MyCycle) Reset() {
 }
 
 func (item *Cyc3MyCycle) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	BuiltinVectorCyc1MyCycleFillRandom(rg, &item.A)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlMaybeTest1/maybeTest1.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlMaybeTest1/maybeTest1.go
index c0cb79e0..62c6b7dd 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlMaybeTest1/maybeTest1.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlMaybeTest1/maybeTest1.go
@@ -57,6 +57,8 @@ func (item *MaybeTest1) Reset() {
 }
 
 func (item *MaybeTest1) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
+	item.N = rg.LimitValue(item.N)
 	item.A.FillRandom(rg)
 	item.B.FillRandom(rg)
 	item.C.FillRandom(rg)
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace11Long/replace11.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace11Long/replace11.go
index 94f85c23..215ad88a 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace11Long/replace11.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace11Long/replace11.go
@@ -31,13 +31,8 @@ func (item *Replace11Long) Reset() {
 }
 
 func (item *Replace11Long) FillRandom(rg *basictl.RandGenerator, nat_n uint32) {
-	var maskK uint32
-	maskK = basictl.RandomUint(rg)
-	maskK = rg.LimitValue(maskK)
-	item.K = 0
-	if maskK&(1<<0) != 0 {
-		item.K |= (1 << 0)
-	}
+	item.K = basictl.RandomUint(rg)
+	item.K = rg.LimitValue(item.K)
 	tlBuiltinTupleReplace11ElemLong.BuiltinTupleReplace11ElemLongFillRandom(rg, &item.A, item.K, nat_n, item.K)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace12/replace12.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace12/replace12.go
index afbbbb52..414226a1 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace12/replace12.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace12/replace12.go
@@ -31,8 +31,13 @@ func (item *Replace12) Reset() {
 }
 
 func (item *Replace12) FillRandom(rg *basictl.RandGenerator) {
-	item.N = basictl.RandomUint(rg)
-	item.N = rg.LimitValue(item.N)
+	var maskN uint32
+	maskN = basictl.RandomUint(rg)
+	maskN = rg.LimitValue(maskN)
+	item.N = 0
+	if maskN&(1<<0) != 0 {
+		item.N |= (1 << 0)
+	}
 	tlBuiltinTupleTuple3Replace12Elem.BuiltinTupleTuple3Replace12ElemFillRandom(rg, &item.A, item.N, item.N)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace14Long/replace14.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace14Long/replace14.go
index a41889ff..827a7329 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace14Long/replace14.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlReplace14Long/replace14.go
@@ -31,13 +31,8 @@ func (item *Replace14Long) Reset() {
 }
 
 func (item *Replace14Long) FillRandom(rg *basictl.RandGenerator, nat_n uint32) {
-	var maskK uint32
-	maskK = basictl.RandomUint(rg)
-	maskK = rg.LimitValue(maskK)
-	item.K = 0
-	if maskK&(1<<0) != 0 {
-		item.K |= (1 << 0)
-	}
+	item.K = basictl.RandomUint(rg)
+	item.K = rg.LimitValue(item.K)
 	tlBuiltinTupleReplace14ElemLong.BuiltinTupleReplace14ElemLongFillRandom(rg, &item.A, item.K, nat_n, item.K)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlTestMaybe2/testMaybe2.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlTestMaybe2/testMaybe2.go
index d1fa5331..30150312 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlTestMaybe2/testMaybe2.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlTestMaybe2/testMaybe2.go
@@ -33,6 +33,7 @@ func (item *TestMaybe2) Reset() {
 }
 
 func (item *TestMaybe2) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
 	item.A.FillRandom(rg)
 	item.G.FillRandom(rg)
 }
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUnionArgsUse/unionArgsUse.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUnionArgsUse/unionArgsUse.go
index f9035759..3c31c9e0 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUnionArgsUse/unionArgsUse.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUnionArgsUse/unionArgsUse.go
@@ -35,6 +35,10 @@ func (item *UnionArgsUse) Reset() {
 }
 
 func (item *UnionArgsUse) FillRandom(rg *basictl.RandGenerator) {
+	item.K = basictl.RandomUint(rg)
+	item.K = rg.LimitValue(item.K)
+	item.N = basictl.RandomUint(rg)
+	item.N = rg.LimitValue(item.N)
 	item.A.FillRandom(rg, item.K)
 	item.B.FillRandom(rg, item.N)
 }
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUseDictUgly/useDictUgly.go b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUseDictUgly/useDictUgly.go
index ee67b345..4ff5fc3b 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUseDictUgly/useDictUgly.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tl/tlUseDictUgly/useDictUgly.go
@@ -64,8 +64,16 @@ func (item *UseDictUgly) Reset() {
 }
 
 func (item *UseDictUgly) FillRandom(rg *basictl.RandGenerator) {
-	item.N = basictl.RandomUint(rg)
-	item.N = rg.LimitValue(item.N)
+	var maskN uint32
+	maskN = basictl.RandomUint(rg)
+	maskN = rg.LimitValue(maskN)
+	item.N = 0
+	if maskN&(1<<0) != 0 {
+		item.N |= (1 << 0)
+	}
+	if maskN&(1<<1) != 0 {
+		item.N |= (1 << 1)
+	}
 	tlBuiltinVectorDictionaryElemUglyIntString.BuiltinVectorDictionaryElemUglyIntStringFillRandom(rg, &item.A, item.N)
 	tlBuiltinVectorDictionaryElemStrangeString.BuiltinVectorDictionaryElemStrangeStringFillRandom(rg, &item.B)
 	tlBuiltinVectorDictionaryElemPairIntIntInt.BuiltinVectorDictionaryElemPairIntIntIntFillRandom(rg, &item.C)
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tla/tlATop2/a.top2.go b/internal/tlcodegen/test/gen/goldmaster/internal/tla/tlATop2/a.top2.go
index 8e4e8b71..18b3507b 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tla/tlATop2/a.top2.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tla/tlATop2/a.top2.go
@@ -32,6 +32,10 @@ func (item *ATop2) Reset() {
 }
 
 func (item *ATop2) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
+	item.N = rg.LimitValue(item.N)
+	item.M = basictl.RandomUint(rg)
+	item.M = rg.LimitValue(item.M)
 	item.C.FillRandom(rg, item.M, item.N, item.N)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbTestMaybe/ab.testMaybe.go b/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbTestMaybe/ab.testMaybe.go
index e907d0d6..96920dc2 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbTestMaybe/ab.testMaybe.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbTestMaybe/ab.testMaybe.go
@@ -39,6 +39,7 @@ func (item *AbTestMaybe) Reset() {
 }
 
 func (item *AbTestMaybe) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
 	item.A.FillRandom(rg)
 	item.B.FillRandom(rg)
 	item.C.FillRandom(rg)
diff --git a/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbUseDictString/ab.useDictString.go b/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbUseDictString/ab.useDictString.go
index d2cc3fc7..298fa09c 100644
--- a/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbUseDictString/ab.useDictString.go
+++ b/internal/tlcodegen/test/gen/goldmaster/internal/tlab/tlAbUseDictString/ab.useDictString.go
@@ -31,6 +31,7 @@ func (item *AbUseDictString) Reset() {
 }
 
 func (item *AbUseDictString) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	tlBuiltinVectorDictionaryFieldString.BuiltinVectorDictionaryFieldStringFillRandom(rg, &item.Tags)
 }
 
@@ -173,6 +174,7 @@ func (item *AbUseDictStringBytes) Reset() {
 }
 
 func (item *AbUseDictStringBytes) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	tlBuiltinVectorDictionaryFieldString.BuiltinVectorDictionaryFieldStringBytesFillRandom(rg, &item.Tags)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/a.top2.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/a.top2.go
index f9a50104..eb3314b7 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/a.top2.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/a.top2.go
@@ -29,6 +29,10 @@ func (item *ATop2) Reset() {
 }
 
 func (item *ATop2) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
+	item.N = rg.LimitValue(item.N)
+	item.M = basictl.RandomUint(rg)
+	item.M = rg.LimitValue(item.M)
 	item.C.FillRandom(rg, item.M, item.N, item.N)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.testMaybe.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.testMaybe.go
index 2ffda737..860965b5 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.testMaybe.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.testMaybe.go
@@ -33,6 +33,7 @@ func (item *AbTestMaybe) Reset() {
 }
 
 func (item *AbTestMaybe) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
 	item.A.FillRandom(rg)
 	item.B.FillRandom(rg)
 	item.C.FillRandom(rg)
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.useDictString.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.useDictString.go
index baf683c2..4da3b915 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.useDictString.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/ab.useDictString.go
@@ -27,6 +27,7 @@ func (item *AbUseDictString) Reset() {
 }
 
 func (item *AbUseDictString) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	BuiltinVectorDictionaryFieldStringFillRandom(rg, &item.Tags)
 }
 
@@ -169,6 +170,7 @@ func (item *AbUseDictStringBytes) Reset() {
 }
 
 func (item *AbUseDictStringBytes) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	BuiltinVectorDictionaryFieldStringBytesFillRandom(rg, &item.Tags)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc2.myCycle.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc2.myCycle.go
index 8737a292..d90632d3 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc2.myCycle.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc2.myCycle.go
@@ -29,6 +29,7 @@ func (item *Cyc2MyCycle) Reset() {
 }
 
 func (item *Cyc2MyCycle) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	item.A.FillRandom(rg)
 	item.B.FillRandom(rg)
 }
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc3.myCycle.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc3.myCycle.go
index ca8b4bf1..e2257345 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc3.myCycle.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/cyc3.myCycle.go
@@ -27,6 +27,7 @@ func (item *Cyc3MyCycle) Reset() {
 }
 
 func (item *Cyc3MyCycle) FillRandom(rg *basictl.RandGenerator) {
+	item.FieldsMask = basictl.RandomUint(rg)
 	BuiltinVectorCyc1MyCycleFillRandom(rg, &item.A)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/maybeTest1.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/maybeTest1.go
index cddc9552..88148b5a 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/maybeTest1.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/maybeTest1.go
@@ -45,6 +45,8 @@ func (item *MaybeTest1) Reset() {
 }
 
 func (item *MaybeTest1) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
+	item.N = rg.LimitValue(item.N)
 	item.A.FillRandom(rg)
 	item.B.FillRandom(rg)
 	item.C.FillRandom(rg)
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace11.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace11.go
index 79302dec..0c777352 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace11.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace11.go
@@ -27,13 +27,8 @@ func (item *Replace11Long) Reset() {
 }
 
 func (item *Replace11Long) FillRandom(rg *basictl.RandGenerator, nat_n uint32) {
-	var maskK uint32
-	maskK = basictl.RandomUint(rg)
-	maskK = rg.LimitValue(maskK)
-	item.K = 0
-	if maskK&(1<<0) != 0 {
-		item.K |= (1 << 0)
-	}
+	item.K = basictl.RandomUint(rg)
+	item.K = rg.LimitValue(item.K)
 	BuiltinTupleReplace11ElemLongFillRandom(rg, &item.A, item.K, nat_n, item.K)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace12.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace12.go
index e87ddaa3..366e058c 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace12.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace12.go
@@ -27,8 +27,13 @@ func (item *Replace12) Reset() {
 }
 
 func (item *Replace12) FillRandom(rg *basictl.RandGenerator) {
-	item.N = basictl.RandomUint(rg)
-	item.N = rg.LimitValue(item.N)
+	var maskN uint32
+	maskN = basictl.RandomUint(rg)
+	maskN = rg.LimitValue(maskN)
+	item.N = 0
+	if maskN&(1<<0) != 0 {
+		item.N |= (1 << 0)
+	}
 	BuiltinTupleTuple3Replace12ElemFillRandom(rg, &item.A, item.N, item.N)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace14.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace14.go
index 5a742a70..66a8a802 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace14.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/replace14.go
@@ -27,13 +27,8 @@ func (item *Replace14Long) Reset() {
 }
 
 func (item *Replace14Long) FillRandom(rg *basictl.RandGenerator, nat_n uint32) {
-	var maskK uint32
-	maskK = basictl.RandomUint(rg)
-	maskK = rg.LimitValue(maskK)
-	item.K = 0
-	if maskK&(1<<0) != 0 {
-		item.K |= (1 << 0)
-	}
+	item.K = basictl.RandomUint(rg)
+	item.K = rg.LimitValue(item.K)
 	BuiltinTupleReplace14ElemLongFillRandom(rg, &item.A, item.K, nat_n, item.K)
 }
 
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/testMaybe2.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/testMaybe2.go
index 657aa456..3d9d397f 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/testMaybe2.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/testMaybe2.go
@@ -29,6 +29,7 @@ func (item *TestMaybe2) Reset() {
 }
 
 func (item *TestMaybe2) FillRandom(rg *basictl.RandGenerator) {
+	item.N = basictl.RandomUint(rg)
 	item.A.FillRandom(rg)
 	item.G.FillRandom(rg)
 }
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/unionArgsUse.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/unionArgsUse.go
index c5a91c35..e850b8d2 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/unionArgsUse.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/unionArgsUse.go
@@ -31,6 +31,10 @@ func (item *UnionArgsUse) Reset() {
 }
 
 func (item *UnionArgsUse) FillRandom(rg *basictl.RandGenerator) {
+	item.K = basictl.RandomUint(rg)
+	item.K = rg.LimitValue(item.K)
+	item.N = basictl.RandomUint(rg)
+	item.N = rg.LimitValue(item.N)
 	item.A.FillRandom(rg, item.K)
 	item.B.FillRandom(rg, item.N)
 }
diff --git a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/useDictUgly.go b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/useDictUgly.go
index 6fd108b0..f537fc6e 100644
--- a/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/useDictUgly.go
+++ b/internal/tlcodegen/test/gen/goldmaster_nosplit/internal/useDictUgly.go
@@ -45,8 +45,16 @@ func (item *UseDictUgly) Reset() {
 }
 
 func (item *UseDictUgly) FillRandom(rg *basictl.RandGenerator) {
-	item.N = basictl.RandomUint(rg)
-	item.N = rg.LimitValue(item.N)
+	var maskN uint32
+	maskN = basictl.RandomUint(rg)
+	maskN = rg.LimitValue(maskN)
+	item.N = 0
+	if maskN&(1<<0) != 0 {
+		item.N |= (1 << 0)
+	}
+	if maskN&(1<<1) != 0 {
+		item.N |= (1 << 1)
+	}
 	BuiltinVectorDictionaryElemUglyIntStringFillRandom(rg, &item.A, item.N)
 	BuiltinVectorDictionaryElemStrangeStringFillRandom(rg, &item.B)
 	BuiltinVectorDictionaryElemPairIntIntIntFillRandom(rg, &item.C)
diff --git a/internal/tlcodegen/type_rw_struct.go b/internal/tlcodegen/type_rw_struct.go
index 5eb9cfd6..032f4771 100644
--- a/internal/tlcodegen/type_rw_struct.go
+++ b/internal/tlcodegen/type_rw_struct.go
@@ -393,8 +393,8 @@ func visit(
 					(*visitResults)[key] = VisitSuccess
 				}
 				natIndexes := make([]int, 0)
-				for i, natParam := range f.t.NatParams {
-					if natParam == natParamName {
+				for i, natParam := range f.natArgs {
+					if natParam.name == natParamName {
 						natIndexes = append(natIndexes, i)
 					}
 				}
@@ -430,8 +430,8 @@ func visit(
 			} else {
 				elementType := i.element.t
 				natIndexes := make([]int, 0)
-				for i, natParam := range elementType.NatParams {
-					if natParam == natParamName {
+				for i, natParam := range i.element.natArgs {
+					if !natParam.isArith && natParam.name == natParamName {
 						natIndexes = append(natIndexes, i)
 					}
 				}