diff --git a/requirements.txt b/requirements.txt
index c7c1d49..8443424 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -11,7 +11,7 @@ async-timeout==3.0.1      # via aiohttp
 attrs==21.2.0             # via aiohttp
 cffi==1.14.5              # via pycares
 chardet==3.0.4            # via aiohttp
-fonttools==4.21.1         # via fdiff (setup.py)
+fonttools==4.22.1         # via fdiff (setup.py)
 idna==3.1                # via yarl
 multidict==5.1.0          # via aiohttp, yarl
 pycares==3.1.1            # via aiodns
diff --git a/tests/testfiles/diff-exe-results.txt b/tests/testfiles/diff-exe-results.txt
index 365534f..d4d793b 100644
--- a/tests/testfiles/diff-exe-results.txt
+++ b/tests/testfiles/diff-exe-results.txt
@@ -235,7 +235,7 @@
 @@ -757,7 +730,7 @@
          <LookupFlag value="0"/>
          <!-- SubTableCount=1 -->
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tests/testfiles/roboto_extdiff_color_expected.txt b/tests/testfiles/roboto_extdiff_color_expected.txt
index e9e9338..13b93f2 100644
--- a/tests/testfiles/roboto_extdiff_color_expected.txt
+++ b/tests/testfiles/roboto_extdiff_color_expected.txt
@@ -235,7 +235,7 @@
 @@ -757,7 +730,7 @@
          <LookupFlag value="0"/>
          <!-- SubTableCount=1 -->
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tests/testfiles/roboto_extdiff_expected.txt b/tests/testfiles/roboto_extdiff_expected.txt
index 5a7fe47..b565240 100644
--- a/tests/testfiles/roboto_extdiff_expected.txt
+++ b/tests/testfiles/roboto_extdiff_expected.txt
@@ -235,7 +235,7 @@
 @@ -757,7 +730,7 @@
          <LookupFlag value="0"/>
          <!-- SubTableCount=1 -->
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tests/testfiles/roboto_udiff_1context_expected.txt b/tests/testfiles/roboto_udiff_1context_expected.txt
index 34b6402..5a71e6d 100644
--- a/tests/testfiles/roboto_udiff_1context_expected.txt
+++ b/tests/testfiles/roboto_udiff_1context_expected.txt
@@ -185,7 +185,7 @@
 -  </post>
  
 @@ -759,3 +732,3 @@
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tests/testfiles/roboto_udiff_color_expected.txt b/tests/testfiles/roboto_udiff_color_expected.txt
index 63b2a66..bf38710 100644
--- a/tests/testfiles/roboto_udiff_color_expected.txt
+++ b/tests/testfiles/roboto_udiff_color_expected.txt
@@ -235,7 +235,7 @@
 @@ -757,7 +730,7 @@
          <LookupFlag value="0"/>
          <!-- SubTableCount=1 -->
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tests/testfiles/roboto_udiff_ex_headpost_expected.txt b/tests/testfiles/roboto_udiff_ex_headpost_expected.txt
index 37e5a2c..b0dc66d 100644
--- a/tests/testfiles/roboto_udiff_ex_headpost_expected.txt
+++ b/tests/testfiles/roboto_udiff_ex_headpost_expected.txt
@@ -176,7 +176,7 @@
 @@ -709,7 +709,7 @@
          <LookupFlag value="0"/>
          <!-- SubTableCount=1 -->
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tests/testfiles/roboto_udiff_expected.txt b/tests/testfiles/roboto_udiff_expected.txt
index 4ec0e98..25f1e6c 100644
--- a/tests/testfiles/roboto_udiff_expected.txt
+++ b/tests/testfiles/roboto_udiff_expected.txt
@@ -235,7 +235,7 @@
 @@ -757,7 +730,7 @@
          <LookupFlag value="0"/>
          <!-- SubTableCount=1 -->
-         <SingleSubst index="0" Format="1">
+         <SingleSubst index="0">
 -          <Substitution in="dollar" out="dollar.smcp"/>
 +          <Substitution in="dollar" out="glyph00010"/>
          </SingleSubst>
diff --git a/tox.ini b/tox.ini
index 9d72c56..e5b377a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py38
+envlist = py39
 
 [testenv]
 commands =