diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 437654947..b4b40f916 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -1736,7 +1736,8 @@ bool Tokenizer::tokenize(std::istream &code,
     arraySize();
 
     // simplify labels and 'case|default'-like syntaxes
-    simplifyLabelsCaseDefault();
+    if (!simplifyLabelsCaseDefault())
+        return false;
 
     // simplify '[;{}] * & ( %any% ) =' to '%any% ='
     simplifyMulAndParens();
@@ -2354,7 +2355,7 @@ void Tokenizer::arraySize()
 
 /** simplify labels and case|default in the code: add a ";" if not already in.*/
 
-void Tokenizer::simplifyLabelsCaseDefault()
+bool Tokenizer::simplifyLabelsCaseDefault()
 {
     bool executablescope = false;
     unsigned int indentlevel = 0;
@@ -2389,15 +2390,19 @@ void Tokenizer::simplifyLabelsCaseDefault()
                 if (Token::Match(tok->next(),"[:{};]"))
                     break;
             }
-            if (tok->next()->str() == ":" && tok->strAt(2) != ";") {
+            if (tok->str() != "case" && tok->next()->str() == ":" && tok->strAt(2) != ";") {
                 tok = tok->next();
                 tok->insertToken(";");
+            } else {
+                syntaxError(tok);
+                return false;
             }
         } else if (Token::Match(tok, "[;{}] %var% : !!;")) {
             tok = tok->tokAt(2);
             tok->insertToken(";");
         }
     }
+    return true;
 }
 
 
diff --git a/lib/tokenize.h b/lib/tokenize.h
index 5cd825d90..186eb95b9 100644
--- a/lib/tokenize.h
+++ b/lib/tokenize.h
@@ -163,8 +163,11 @@ public:
     /** Insert array size where it isn't given */
     void arraySize();
 
-    /** Simplify labels and 'case|default' syntaxes */
-    void simplifyLabelsCaseDefault();
+    /** Simplify labels and 'case|default' syntaxes.
+      * @return true if found nothing or the syntax is correct.
+      *         false if syntax is found to be wrong.
+      */
+    bool simplifyLabelsCaseDefault();
 
     /** Remove macros in global scope */
     void removeMacrosInGlobalScope();
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index c7a18de52..a4b8450e6 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -66,6 +66,7 @@ private:
         TEST_CASE(wrong_syntax3); // #3544
         TEST_CASE(wrong_syntax4); // #3618
         TEST_CASE(wrong_syntax_if_macro);  // #2518 - if MACRO()
+        TEST_CASE(wrong_syntax_case_default);
         TEST_CASE(garbageCode);
 
         TEST_CASE(foreach);     // #3690
@@ -722,6 +723,20 @@ private:
         ASSERT_EQUALS("[test.cpp:1]: (error) syntax error\n", errout.str());
     }
 
+    void wrong_syntax_case_default() {
+        {
+            //ticket #4234
+            tokenizeAndStringify("( ) { switch break ; { switch ( x ) { case } y break ; : } }");
+            ASSERT_EQUALS("[test.cpp:1]: (error) syntax error\n", errout.str());
+        }
+
+        {
+            //ticket #4267
+            tokenizeAndStringify("f ( ) { switch break; { switch ( x ) { case } case break; -6: ( ) ; } }");
+            ASSERT_EQUALS("[test.cpp:1]: (error) syntax error\n", errout.str());
+        }
+    }
+
     void garbageCode() {
         tokenizeAndStringify("struct x foo_t; foo_t typedef y;");
     }