diff --git a/lang/m2/comp/LLlex.c b/lang/m2/comp/LLlex.c
index 2f4887342..2884c0291 100644
--- a/lang/m2/comp/LLlex.c
+++ b/lang/m2/comp/LLlex.c
@@ -383,6 +383,7 @@ lexwarning("Character constant out of range");
 			}
 		}
 
+		*np++ = '\0';
 		PushBack(ch);
 
 		if (np >= &buf[NUMSIZE]) {