diff --git a/cpufeatures/src/aarch64.rs b/cpufeatures/src/aarch64.rs
index 2305d898..4248a754 100644
--- a/cpufeatures/src/aarch64.rs
+++ b/cpufeatures/src/aarch64.rs
@@ -117,6 +117,9 @@ macro_rules! check {
                 && $crate::aarch64::sysctlbyname(b"hw.optional.armv8_2_sha3\0")
         }
     };
+    ("sm4") => {
+        false
+    };
 }
 
 /// Apple helper function for calling `sysctlbyname`.