diff --git a/src/librustc/dep_graph/dep_node.rs b/src/librustc/dep_graph/dep_node.rs
index b061663148d4d..92efeb7fd8629 100644
--- a/src/librustc/dep_graph/dep_node.rs
+++ b/src/librustc/dep_graph/dep_node.rs
@@ -257,11 +257,11 @@ macro_rules! define_dep_nodes {
             pub fn extract_def_id(&self, tcx: TyCtxt) -> Option<DefId> {
                 if self.kind.can_reconstruct_query_key() {
                     let def_path_hash = DefPathHash(self.hash);
-                    tcx.def_path_hash_to_def_id
-                       .as_ref()
-                       .unwrap()
-                       .get(&def_path_hash)
-                       .cloned()
+                    if let Some(ref def_path_map) = tcx.def_path_hash_to_def_id.as_ref() {
+                        def_path_map.get(&def_path_hash).cloned()
+                    } else {
+                       None
+                    }
                 } else {
                     None
                 }
diff --git a/src/test/run-pass/rustc-rust-log.rs b/src/test/run-pass/rustc-rust-log.rs
new file mode 100644
index 0000000000000..629387d4cb11d
--- /dev/null
+++ b/src/test/run-pass/rustc-rust-log.rs
@@ -0,0 +1,13 @@
+// Copyright 2017 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.
+
+// rustc-env:RUST_LOG=debug
+
+fn main() {}