diff --git a/compiler/rustc_passes/src/check_const.rs b/compiler/rustc_passes/src/check_const.rs
index 4062862ad747c..116aaf4834981 100644
--- a/compiler/rustc_passes/src/check_const.rs
+++ b/compiler/rustc_passes/src/check_const.rs
@@ -198,8 +198,8 @@ impl<'tcx> Visitor<'tcx> for CheckConstVisitor<'tcx> {
             of_trait: Some(trait_ref),
             ..
         }) = item.kind
+            && let Some(def_id) = trait_ref.trait_def_id()
         {
-            let def_id = trait_ref.trait_def_id().unwrap();
             let source_map = tcx.sess.source_map();
             if !tcx.has_attr(def_id, sym::const_trait) {
                 tcx.sess
diff --git a/src/test/ui/rfc-2632-const-trait-impl/issue-102156.rs b/src/test/ui/rfc-2632-const-trait-impl/issue-102156.rs
new file mode 100644
index 0000000000000..fe4e910813013
--- /dev/null
+++ b/src/test/ui/rfc-2632-const-trait-impl/issue-102156.rs
@@ -0,0 +1,15 @@
+#![feature(allocator_api)]
+#![feature(const_trait_impl)]
+
+use core::convert::{From, TryFrom};
+//~^ ERROR
+//~| ERROR
+
+use std::pin::Pin;
+use std::alloc::Allocator;
+impl<T: ?Sized, A: Allocator> const From<Box<T, A>> for Pin<Box<T, A>>
+where
+    A: 'static,
+{}
+
+pub fn main() {}
diff --git a/src/test/ui/rfc-2632-const-trait-impl/issue-102156.stderr b/src/test/ui/rfc-2632-const-trait-impl/issue-102156.stderr
new file mode 100644
index 0000000000000..8bf00eaff1fb9
--- /dev/null
+++ b/src/test/ui/rfc-2632-const-trait-impl/issue-102156.stderr
@@ -0,0 +1,19 @@
+error[E0433]: failed to resolve: maybe a missing crate `core`?
+  --> $DIR/issue-102156.rs:4:5
+   |
+LL | use core::convert::{From, TryFrom};
+   |     ^^^^ maybe a missing crate `core`?
+   |
+   = help: consider adding `extern crate core` to use the `core` crate
+
+error[E0433]: failed to resolve: maybe a missing crate `core`?
+  --> $DIR/issue-102156.rs:4:5
+   |
+LL | use core::convert::{From, TryFrom};
+   |     ^^^^ maybe a missing crate `core`?
+   |
+   = help: consider adding `extern crate core` to use the `core` crate
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0433`.