diff --git a/clippy_utils/src/qualify_min_const_fn.rs b/clippy_utils/src/qualify_min_const_fn.rs
index 58f7742ab..9f6adf3e3 100644
--- a/clippy_utils/src/qualify_min_const_fn.rs
+++ b/clippy_utils/src/qualify_min_const_fn.rs
@@ -176,6 +176,9 @@ fn check_rvalue<'tcx>(
             // FIXME(dyn-star)
             unimplemented!()
         },
+        Rvalue::Cast(CastKind::Transmute, _, _) => {
+            Err((span, "transmute can attempt to turn pointers into integers, so is unstable in const fn".into()))
+        },
         // binops are fine on integers
         Rvalue::BinaryOp(_, box (lhs, rhs)) | Rvalue::CheckedBinaryOp(_, box (lhs, rhs)) => {
             check_operand(tcx, lhs, span, body)?;