diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 6c78aba93..7b4dc00cf 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -3320,9 +3320,17 @@ bool Tokenizer::simplifySizeof()
             for (Token *tempToken = tok->next(); tempToken; tempToken = tempToken->next()) {
                 if (tempToken->str() == "(")
                     ++parlevel;
-                else if (tempToken->str() == ")")
+                else if (tempToken->str() == ")") {
                     --parlevel;
-                if (Token::Match(tempToken, "%var%")) {
+                    if (parlevel == 0 && !Token::Match(tempToken, ") . %var%")) {
+                        // Ok, we should be clean. Add ) after tempToken
+                        tok->insertToken("(");
+                        tempToken->insertToken(")");
+                        Token::createMutualLinks(tok->next(), tempToken->next());
+                        break;
+                    }
+                }
+                if (parlevel == 0 && Token::Match(tempToken, "%var%")) {
                     while (tempToken && tempToken->next() && tempToken->next()->str() == "[") {
                         tempToken = tempToken->next()->link();
                     }
diff --git a/test/testsimplifytokens.cpp b/test/testsimplifytokens.cpp
index bf9d2dbf5..ea0acc2bc 100644
--- a/test/testsimplifytokens.cpp
+++ b/test/testsimplifytokens.cpp
@@ -1325,6 +1325,9 @@ private:
                                 " int aa ; aa = sizeof ( * ( * a ) . b ) ; "
                                 "}";
         ASSERT_EQUALS(expected, tok(code));
+
+        // #5064 - sizeof !! (a == 1);
+        ASSERT_EQUALS("sizeof ( ! ! ( a == 1 ) ) ;", tok("sizeof !!(a==1);"));
     }
 
     void sizeof15() {