diff --git a/src/cindent.c b/src/cindent.c
index 6289422..cf18441 100644
--- a/src/cindent.c
+++ b/src/cindent.c
@@ -4108,7 +4108,8 @@
 		}
 		else
 		    // TODO: multi-byte
-		    if (keytyped == (int)p[-1] || (icase && keytyped < 256
+		    if (keytyped == (int)p[-1] || (icase
+				&& keytyped < 256 && keytyped >= 0
 			 && TOLOWER_LOC(keytyped) == TOLOWER_LOC((int)p[-1])))
 		{
 		    line = ml_get_cursor();