4 files changed, 8 insertions, 0 deletions
diff --git a/library/std/tests/floats/f128.rs b/library/std/tests/floats/f128.rs
index df28e8129dd..677738bac8f 100644
--- a/library/std/tests/floats/f128.rs
+++ b/library/std/tests/floats/f128.rs
@@ -112,6 +112,8 @@ fn test_nan() {
     assert!(!nan.is_sign_negative());
     assert!(!nan.is_normal());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f128::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]
diff --git a/library/std/tests/floats/f16.rs b/library/std/tests/floats/f16.rs
index 1a90f00aecc..0fc4df8115a 100644
--- a/library/std/tests/floats/f16.rs
+++ b/library/std/tests/floats/f16.rs
@@ -95,6 +95,8 @@ fn test_nan() {
     assert!(!nan.is_sign_negative());
     assert!(!nan.is_normal());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f16::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]
diff --git a/library/std/tests/floats/f32.rs b/library/std/tests/floats/f32.rs
index d99b03cb255..9af23afc5bb 100644
--- a/library/std/tests/floats/f32.rs
+++ b/library/std/tests/floats/f32.rs
@@ -72,6 +72,8 @@ fn test_nan() {
     assert!(nan.is_sign_positive());
     assert!(!nan.is_sign_negative());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f32::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]
diff --git a/library/std/tests/floats/f64.rs b/library/std/tests/floats/f64.rs
index 611670751bb..de9c27eb33d 100644
--- a/library/std/tests/floats/f64.rs
+++ b/library/std/tests/floats/f64.rs
@@ -60,6 +60,8 @@ fn test_nan() {
     assert!(nan.is_sign_positive());
     assert!(!nan.is_sign_negative());
     assert_eq!(Fp::Nan, nan.classify());
+    // Ensure the quiet bit is set.
+    assert!(nan.to_bits() & (1 << (f64::MANTISSA_DIGITS - 2)) != 0);
 }
 
 #[test]