diff --git a/src/tools/moc/preprocessor.cpp b/src/tools/moc/preprocessor.cpp
index 32c94639ab..9a06fb38d0 100644
--- a/src/tools/moc/preprocessor.cpp
+++ b/src/tools/moc/preprocessor.cpp
@@ -1109,19 +1109,18 @@ void Preprocessor::preprocess(const QByteArray &filename, Symbols &preprocessed)
         }
         case PP_DEFINE:
         {
-            next(IDENTIFIER);
+            next();
             QByteArray name = lexem();
+            if (name.isEmpty() || !is_ident_start(name[0]))
+                error();
             Macro macro;
             macro.isVariadic = false;
-            Token t = next();
-            if (t == LPAREN) {
+            if (test(LPAREN)) {
                 // we have a function macro
                 macro.isFunction = true;
                 parseDefineArguments(&macro);
-            } else if (t == PP_WHITESPACE){
-                macro.isFunction = false;
             } else {
-                error("Moc: internal error");
+                macro.isFunction = false;
             }
             int start = index;
             until(PP_NEWLINE);
@@ -1160,7 +1159,7 @@ void Preprocessor::preprocess(const QByteArray &filename, Symbols &preprocessed)
             continue;
         }
         case PP_UNDEF: {
-            next(IDENTIFIER);
+            next();
             QByteArray name = lexem();
             until(PP_NEWLINE);
             macros.remove(name);
diff --git a/tests/auto/tools/moc/parse-defines.h b/tests/auto/tools/moc/parse-defines.h
index 6100bf67ad..7b0fa29d7c 100644
--- a/tests/auto/tools/moc/parse-defines.h
+++ b/tests/auto/tools/moc/parse-defines.h
@@ -146,6 +146,15 @@ signals:
 
 #undef QString
 
+#ifdef Q_MOC_RUN
+// Normaly, redefining keywords is forbidden, but we should not abort parsing
+#define and    &&
+#define and_eq &=
+#define bitand  &
+#define true 1
+#undef true
+#endif
+
 PD_END_NAMESPACE
 
 #endif