diff --git a/core/src/num/f32.rs b/core/src/num/f32.rs
index 4c2a4ee3b3255..d0eb6bb3f2879 100644
--- a/core/src/num/f32.rs
+++ b/core/src/num/f32.rs
@@ -415,6 +415,7 @@ impl f32 {
     /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
     /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
+    #[cfg_attr(not(test), rustc_diagnostic_item = "f32_epsilon")]
     pub const EPSILON: f32 = 1.19209290e-07_f32;
 
     /// Smallest finite `f32` value.
diff --git a/core/src/num/f64.rs b/core/src/num/f64.rs
index 87fb5fe7ebeea..4bc275ad14786 100644
--- a/core/src/num/f64.rs
+++ b/core/src/num/f64.rs
@@ -414,6 +414,7 @@ impl f64 {
     /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
     /// [`MANTISSA_DIGITS`]: f64::MANTISSA_DIGITS
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
+    #[cfg_attr(not(test), rustc_diagnostic_item = "f64_epsilon")]
     pub const EPSILON: f64 = 2.2204460492503131e-16_f64;
 
     /// Smallest finite `f64` value.