diff --git a/library/std/src/f128/tests.rs b/library/std/src/f128/tests.rs
index 7051c051bf723..1810efc994deb 100644
--- a/library/std/src/f128/tests.rs
+++ b/library/std/src/f128/tests.rs
@@ -53,7 +53,21 @@ macro_rules! assert_f128_biteq {
 
 #[test]
 fn test_num_f128() {
-    test_num(10f128, 2f128);
+    // FIXME(f16_f128): replace with a `test_num` call once the required `fmodl`/`fmodf128` function is available on all platforms.
+    let ten = 10f128;
+    let two = 2f128;
+    assert_eq!(ten.add(two), ten + two);
+    assert_eq!(ten.sub(two), ten - two);
+    assert_eq!(ten.mul(two), ten * two);
+    assert_eq!(ten.div(two), ten / two);
+}
+
+#[test]
+#[cfg(reliable_f128_math)]
+fn test_num_f128_rem() {
+    let ten = 10f128;
+    let two = 2f128;
+    assert_eq!(ten.rem(two), ten % two);
 }
 
 #[test]