diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 8e2691c8a27a1..f32df13ad2a36 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -3042,15 +3042,17 @@ pub fn adjust_ty(cx: ctxt,
         Some(@AutoDerefRef(ref adj)) => {
             let mut adjusted_ty = unadjusted_ty;
 
-            for uint::range(0, adj.autoderefs) |i| {
-                match ty::deref(cx, adjusted_ty, true) {
-                    Some(mt) => { adjusted_ty = mt.ty; }
-                    None => {
-                        cx.sess.span_bug(
-                            span,
-                            fmt!("The %uth autoderef failed: %s",
-                                 i, ty_to_str(cx,
-                                              adjusted_ty)));
+            if (!ty::type_is_error(adjusted_ty)) {
+                for uint::range(0, adj.autoderefs) |i| {
+                    match ty::deref(cx, adjusted_ty, true) {
+                        Some(mt) => { adjusted_ty = mt.ty; }
+                        None => {
+                            cx.sess.span_bug(
+                                span,
+                                fmt!("The %uth autoderef failed: %s",
+                                     i, ty_to_str(cx,
+                                                  adjusted_ty)));
+                        }
                     }
                 }
             }
diff --git a/src/librustc/middle/typeck/check/regionck.rs b/src/librustc/middle/typeck/check/regionck.rs
index 58749b92ddcd4..9cfa0187ab658 100644
--- a/src/librustc/middle/typeck/check/regionck.rs
+++ b/src/librustc/middle/typeck/check/regionck.rs
@@ -460,6 +460,10 @@ fn constrain_call(rcx: @mut Rcx,
     debug!("constrain_call(call_expr=%s, implicitly_ref_args=%?)",
            call_expr.repr(tcx), implicitly_ref_args);
     let callee_ty = rcx.resolve_node_type(callee_id);
+    if ty::type_is_error(callee_ty) {
+        // Bail, as function type is unknown
+        return;
+    }
     let fn_sig = ty::ty_fn_sig(callee_ty);
 
     // `callee_region` is the scope representing the time in which the
@@ -1108,6 +1112,12 @@ pub mod guarantor {
      -> ExprCategorizationType {
         let mut ct = ct;
         let tcx = rcx.fcx.ccx.tcx;
+
+        if (ty::type_is_error(ct.ty)) {
+            ct.cat.pointer = NotPointer;
+            return ct;
+        }
+
         for uint::range(0, autoderefs) |_| {
             ct.cat.guarantor = guarantor_of_deref(&ct.cat);
 
diff --git a/src/test/compile-fail/unconstrained-none.rs b/src/test/compile-fail/unconstrained-none.rs
new file mode 100644
index 0000000000000..7993df80b8d1b
--- /dev/null
+++ b/src/test/compile-fail/unconstrained-none.rs
@@ -0,0 +1,15 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Issue #5062
+
+fn main() {
+    fmt!("%?", None); //~ ERROR cannot determine a type for this expression: unconstrained type
+}
diff --git a/src/test/compile-fail/unconstrained-ref.rs b/src/test/compile-fail/unconstrained-ref.rs
new file mode 100644
index 0000000000000..80bd83caf3250
--- /dev/null
+++ b/src/test/compile-fail/unconstrained-ref.rs
@@ -0,0 +1,17 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct S<'self, T> {
+    o: &'self Option<T>
+}
+
+fn main() {
+    S { o: &None }; //~ ERROR cannot determine a type for this expression: unconstrained type
+}