diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index d79a2fd05..f55423a45 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -4079,7 +4079,7 @@ bool Tokenizer::simplifyKnownVariables()
                         for (const Token *tok4 = tok3; tok4 && tok4 != endpar; tok4 = tok4->next())
                         {
                             if (Token::Match(tok4, "++|-- %varid%", varid) ||
-                                Token::Match(tok4, "%varid% ++|--", varid))
+                                Token::Match(tok4, "%varid% ++|--|=", varid))
                             {
                                 bailout = true;
                                 break;
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index b30b05361..547566aab 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -93,6 +93,7 @@ private:
         TEST_CASE(simplifyKnownVariables16);
         TEST_CASE(simplifyKnownVariables17);
         TEST_CASE(simplifyKnownVariables18);
+        TEST_CASE(simplifyKnownVariables19);
 
         TEST_CASE(match1);
 
@@ -979,6 +980,14 @@ private:
             simplifyKnownVariables(code));
     }
 
+    void simplifyKnownVariables19()
+    {
+        const char code[] = "void f ( ) { int i=0; do { if (i>0) { a(); } i=b(); } while (i != 12); }";
+        ASSERT_EQUALS(
+            "void f ( ) { int i ; i = 0 ; do { if ( 0 < i ) { a ( ) ; } i = b ( ) ; } while ( i != 12 ) ; }",
+            simplifyKnownVariables(code));
+    }
+
     void match1()
     {
         // Match "%var% | %var%"