diff --git a/lib/YAML/PP/Lexer.pm b/lib/YAML/PP/Lexer.pm
index 459c53de..b63beb59 100644
--- a/lib/YAML/PP/Lexer.pm
+++ b/lib/YAML/PP/Lexer.pm
@@ -42,6 +42,8 @@ sub context { return $_[0]->{context} }
 sub set_context { $_[0]->{context} = $_[1] }
 sub flowcontext { return $_[0]->{flowcontext} }
 sub set_flowcontext { $_[0]->{flowcontext} = $_[1] }
+sub block { return $_[0]->{block} }
+sub set_block { $_[0]->{block} = $_[1] }
 
 my $RE_WS = '[\t ]';
 my $RE_LB = '[\r\n]';
@@ -141,6 +143,7 @@ sub fetch_next_line {
         $self->set_next_line(undef);
         return;
     }
+    $self->set_block(1);
     $self->inc_line;
     $line =~ m/\A( *)([^\r\n]*)([\r\n]|\z)/ or die "Unexpected";
     $next_line = [ $1,  $2, $3 ];
@@ -278,7 +281,15 @@ sub _fetch_next_tokens {
         }
         elsif ($COLON_DASH_QUESTION{ $first }) {
             my $token_name = $TOKEN_NAMES{ $first };
-            if ($$yaml =~ s/\A\Q$first\E(?:($RE_WS+)|\z)//) {
+            if ($$yaml =~ s/\A\Q$first\E($RE_WS+|\z)//) {
+                if (not $self->flowcontext and not $self->block) {
+                    $self->push_tokens(\@tokens);
+                    $self->exception("Tabs can not be used for indentation");
+                }
+                my $after = $1;
+                if ($after =~ tr/\t//) {
+                    $self->set_block(0);
+                }
                 my $token_name = $TOKEN_NAMES{ $first };
                 push @tokens, ( $token_name => $first, $self->line );
                 if (not defined $1) {
diff --git a/t/11.parse-invalid.t b/t/11.parse-invalid.t
index 960a8c55..1ca889a2 100644
--- a/t/11.parse-invalid.t
+++ b/t/11.parse-invalid.t
@@ -43,6 +43,8 @@ my %skip_events = (
     '4H7K' => 1,
     BS4K => 1,
     EB22 => 1,
+    i037 => 1,
+    i038 => 1,
 );
 
 
diff --git a/t/invalid/i037/=== b/t/invalid/i037/===
new file mode 100644
index 00000000..cb38fbdc
--- /dev/null
+++ b/t/invalid/i037/===
@@ -0,0 +1 @@
+Tabs in various contexts
diff --git a/t/invalid/i037/in.yaml b/t/invalid/i037/in.yaml
new file mode 100644
index 00000000..0806e5a9
--- /dev/null
+++ b/t/invalid/i037/in.yaml
@@ -0,0 +1 @@
+-	-
diff --git a/t/invalid/i037/test.event b/t/invalid/i037/test.event
new file mode 100644
index 00000000..b8e31a8b
--- /dev/null
+++ b/t/invalid/i037/test.event
@@ -0,0 +1,2 @@
++STR
++DOC
diff --git a/t/invalid/i038/=== b/t/invalid/i038/===
new file mode 100644
index 00000000..cb38fbdc
--- /dev/null
+++ b/t/invalid/i038/===
@@ -0,0 +1 @@
+Tabs in various contexts
diff --git a/t/invalid/i038/in.yaml b/t/invalid/i038/in.yaml
new file mode 100644
index 00000000..ec674043
--- /dev/null
+++ b/t/invalid/i038/in.yaml
@@ -0,0 +1 @@
+- 	-
diff --git a/t/invalid/i038/test.event b/t/invalid/i038/test.event
new file mode 100644
index 00000000..b8e31a8b
--- /dev/null
+++ b/t/invalid/i038/test.event
@@ -0,0 +1,2 @@
++STR
++DOC
diff --git a/t/valid/v032/=== b/t/valid/v032/===
new file mode 100644
index 00000000..cb38fbdc
--- /dev/null
+++ b/t/valid/v032/===
@@ -0,0 +1 @@
+Tabs in various contexts
diff --git a/t/valid/v032/in.yaml b/t/valid/v032/in.yaml
new file mode 100644
index 00000000..763ef1b7
--- /dev/null
+++ b/t/valid/v032/in.yaml
@@ -0,0 +1 @@
+-	-1
diff --git a/t/valid/v032/out.yaml b/t/valid/v032/out.yaml
new file mode 100644
index 00000000..9572567a
--- /dev/null
+++ b/t/valid/v032/out.yaml
@@ -0,0 +1 @@
+- -1
diff --git a/t/valid/v032/test.event b/t/valid/v032/test.event
new file mode 100644
index 00000000..8d71c76c
--- /dev/null
+++ b/t/valid/v032/test.event
@@ -0,0 +1,7 @@
++STR
++DOC
++SEQ
+=VAL :-1
+-SEQ
+-DOC
+-STR