diff --git a/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspLexer.java b/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspLexer.java
--- a/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspLexer.java
+++ b/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspLexer.java
@@ -799,7 +799,7 @@
             case LT_EM_DOUBLE_DASH: return GspTokenId.COMMENT_HTML_STYLE_START;
             case LT_PC_DOUBLE_DASH: return GspTokenId.COMMENT_JSP_STYLE_START;
             case PC_CB_DOUBLE_DASH: return GspTokenId.COMMENT_GSP_STYLE_START;
-            default: return null;
+            default: return GspTokenId.ERROR;
         }
     }
 
diff --git a/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspTokenId.java b/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspTokenId.java
--- a/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspTokenId.java
+++ b/groovy.gsp/src/org/netbeans/modules/groovy/gsp/lexer/GspTokenId.java
@@ -62,6 +62,7 @@
 
     HTML("html"),
     WHITESPACE("whitespace"),
+    ERROR("error"),
 
     // GTags tokens
     GTAG_OPENING_START("gtag"),                      // <g:    ...