diff --git a/arch/AArch64/mapping.c b/arch/AArch64/mapping.c
index f02b85f..0250705 100644
--- a/arch/AArch64/mapping.c
+++ b/arch/AArch64/mapping.c
@@ -3502,14 +3502,18 @@
 	if (id >= ARM64_INS_MAX)
 		return NULL;
 
-	// try with alias insn first
+	if (id < ARR_SIZE(insn_name_maps))
+		return insn_name_maps[id].name;
+
+	// then find alias insn
 	int i;
 	for (i = 0; i < ARR_SIZE(alias_insn_name_maps); i++) {
 		if (alias_insn_name_maps[i].id == id)
 			return alias_insn_name_maps[i].name;
 	}
 
-	return insn_name_maps[id].name;
+	// not found
+	return NULL;
 }
 
 // map instruction name to public instruction ID