diff --git a/src/driver.rs b/src/driver.rs
index 22271460b02..0166f9ea5ba 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -307,7 +307,7 @@ fn codegen_mono_items<'tcx>(
         }
 
         for (mono_item, (linkage, visibility)) in mono_items {
-            crate::unimpl::try_unimpl(tcx, mono_item.to_string(tcx, true), || {
+            crate::unimpl::try_unimpl(tcx, || {
                 let linkage = crate::linkage::get_clif_linkage(mono_item, linkage, visibility);
                 trans_mono_item(&mut cx, mono_item, linkage);
             });
diff --git a/src/unimpl.rs b/src/unimpl.rs
index 3e7dddc6445..b668235e75e 100644
--- a/src/unimpl.rs
+++ b/src/unimpl.rs
@@ -1,14 +1,8 @@
 //! The unimpl! macro is defined here. It is used to generate
 //! a non-fatal error on not yet implemented things.
 
-use std::cell::RefCell;
-
 use rustc::ty::TyCtxt;
 
-thread_local! {
-    static CURRENT_MSG: RefCell<String> = RefCell::new(String::new());
-}
-
 // Just public, because of the unimpl macro
 #[doc(hidden)]
 pub struct NonFatal(pub String);
@@ -20,21 +14,15 @@
     panic!(NonFatal(format!($($tt)*)));
 }
 
-pub fn try_unimpl(tcx: TyCtxt, msg: String, f: impl FnOnce()) {
-    CURRENT_MSG.with(|current_msg| {
-        let old = std::mem::replace(&mut *current_msg.borrow_mut(), msg);
+pub fn try_unimpl(tcx: TyCtxt, f: impl FnOnce()) {
+    let res = ::std::panic::catch_unwind(::std::panic::AssertUnwindSafe(|| f()));
 
-        let res = ::std::panic::catch_unwind(::std::panic::AssertUnwindSafe(|| f()));
-
-        if let Err(err) = res {
-            match err.downcast::<NonFatal>() {
-                Ok(non_fatal) => {
-                    tcx.sess.err(&format!("at {}: {}", current_msg.borrow(), non_fatal.0));
-                }
-                Err(err) => ::std::panic::resume_unwind(err),
+    if let Err(err) = res {
+        match err.downcast::<NonFatal>() {
+            Ok(non_fatal) => {
+                tcx.sess.err(&non_fatal.0);
             }
+            Err(err) => ::std::panic::resume_unwind(err),
         }
-
-        *current_msg.borrow_mut() = old;
-    });
+    }
 }