diff --git a/sys/dev/aic7xxx/aicasm/aicasm_gram.y b/sys/dev/aic7xxx/aicasm/aicasm_gram.y
index d0bc6714acd..91425f38c30 100644
--- a/sys/dev/aic7xxx/aicasm/aicasm_gram.y
+++ b/sys/dev/aic7xxx/aicasm/aicasm_gram.y
@@ -623,6 +623,11 @@ immediate_or_a:
 	expression
 	{
 		$$ = $1;
+		if ($$.value == 0) {
+			stop("Immediate value of 0 not valid for opcode",
+			     EX_DATAERR);
+			/* NOTREACHED */
+		}
 	}
 |	T_A
 	{