diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index b97dd7751..2a1092196 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -7465,6 +7465,11 @@ void Tokenizer::simplifyEnum()
                     enumName = tok1;
                     lastValue = 0;
                     tok1 = tok1->tokAt(2);
+                    if (tok1->str() == "," || tok1->str() == "}") {
+                        syntaxError(tok1);
+                        break;
+                    }
+
                     enumValueStart = tok1;
                     enumValueEnd = tok1;
                     int level = 0;
diff --git a/test/testsimplifytokens.cpp b/test/testsimplifytokens.cpp
index 5cf74a1d5..cf5254d2e 100644
--- a/test/testsimplifytokens.cpp
+++ b/test/testsimplifytokens.cpp
@@ -374,6 +374,7 @@ private:
         TEST_CASE(enum42); // ticket #5182 (template function call in enum value)
         TEST_CASE(enumscope1); // ticket #3949
         TEST_CASE(duplicateDefinition); // ticket #3565
+        TEST_CASE(invalid_enum); // #5600
 
         // remove "std::" on some standard functions
         TEST_CASE(removestd);
@@ -7150,6 +7151,18 @@ private:
         ASSERT_EQUALS(false, tokenizer.duplicateDefinition(&x_token, tokenizer.tokens()));
     }
 
+    void invalid_enum() { // #5600: missing include causes invalid enum
+        const char code [] = "enum {\n"
+                             "    NUM_OPCODES = \n"
+                             // #include "definition"
+                             "};\n"
+                             "struct bytecode {};\n"
+                             "jv jq_next() { opcode = ((opcode) +NUM_OPCODES);\n"
+                             "}";
+        checkSimplifyEnum(code);
+        ASSERT_EQUALS("[test.cpp:3]: (error) syntax error\n", errout.str());
+    }
+
     void removestd() {
         ASSERT_EQUALS("; strcpy ( a , b ) ;", tok("; std::strcpy(a,b);"));
         ASSERT_EQUALS("; strcat ( a , b ) ;", tok("; std::strcat(a,b);"));