diff --git a/src/core/org/luaj/vm2/compiler/LexState.java b/src/core/org/luaj/vm2/compiler/LexState.java
index 58864110..1fbfd38a 100644
--- a/src/core/org/luaj/vm2/compiler/LexState.java
+++ b/src/core/org/luaj/vm2/compiler/LexState.java
@@ -198,7 +198,7 @@ public class LexState extends Constants {
 	}
 	
 	private boolean isspace(int c) {
-		return (c <= ' ');
+		return (c >= 0 && c <= ' ');
 	}