diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index d042aaf3084d6..509a8b63743c5 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -1130,7 +1130,10 @@ extern "rust-intrinsic" {
     /// may lead to unexpected and unstable compilation results. This makes `transmute` **incredibly
     /// unsafe**. `transmute` should be the absolute last resort.
     ///
-    /// Transmuting pointers to integers in a `const` context is [undefined behavior][ub].
+    /// Transmuting pointers *to* integers in a `const` context is [undefined behavior][ub],
+    /// unless the pointer was originally created *from* an integer.
+    /// (That includes this function specifically, integer-to-pointer casts, and helpers like [`invalid`][crate::ptr::invalid],
+    /// but also semantically-equivalent conversions such as punning through `repr(C)` union fields.)
     /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
     /// (And even outside `const`, such transmutation is touching on many unspecified aspects of the
     /// Rust memory model and should be avoided. See below for alternatives.)