diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 71274c4fdaa4e..872304c664980 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -5131,25 +5131,30 @@ impl<'a> Parser<'a> {
             }
             let mut err = self.diagnostic().struct_span_err(id_sp,
                 "cannot declare a new module at this location");
-            let this_module = match self.directory.path.file_name() {
-                Some(file_name) => file_name.to_str().unwrap().to_owned(),
-                None => self.root_module_name.as_ref().unwrap().clone(),
-            };
-            err.span_note(id_sp,
-                          &format!("maybe move this module `{0}` to its own directory \
-                                     via `{0}/mod.rs`",
-                                    this_module));
+            if id_sp != syntax_pos::DUMMY_SP {
+                let src_path = PathBuf::from(self.sess.codemap().span_to_filename(id_sp));
+                if let Some(stem) = src_path.clone().file_stem() {
+                    let mut dest_path = src_path.clone();
+                    dest_path.set_file_name(stem);
+                    dest_path.push("mod.rs");
+                    err.span_note(id_sp,
+                                  &format!("maybe move this module `{}` to its own \
+                                            directory via `{}`", src_path.to_string_lossy(),
+                                           dest_path.to_string_lossy()));
+                }
+            }
             if paths.path_exists {
                 err.span_note(id_sp,
                               &format!("... or maybe `use` the module `{}` instead \
                                         of possibly redeclaring it",
                                        paths.name));
-                Err(err)
-            } else {
-                Err(err)
             }
+            Err(err)
         } else {
-            paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
+            match paths.result {
+                Ok(succ) => Ok(succ),
+                Err(err) => Err(self.span_fatal_err(id_sp, err)),
+            }
         }
     }
 
diff --git a/src/test/compile-fail/auxiliary/foo/bar.rs b/src/test/compile-fail/auxiliary/foo/bar.rs
new file mode 100644
index 0000000000000..4b6b4f5ebf82f
--- /dev/null
+++ b/src/test/compile-fail/auxiliary/foo/bar.rs
@@ -0,0 +1,11 @@
+// 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.
+
+pub mod baz;
diff --git a/src/test/compile-fail/auxiliary/foo/mod.rs b/src/test/compile-fail/auxiliary/foo/mod.rs
new file mode 100644
index 0000000000000..6d77fb60a35de
--- /dev/null
+++ b/src/test/compile-fail/auxiliary/foo/mod.rs
@@ -0,0 +1,11 @@
+// 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.
+
+pub mod bar;
diff --git a/src/test/compile-fail/invalid-module-declaration.rs b/src/test/compile-fail/invalid-module-declaration.rs
new file mode 100644
index 0000000000000..c15cfb8cc8e22
--- /dev/null
+++ b/src/test/compile-fail/invalid-module-declaration.rs
@@ -0,0 +1,20 @@
+// Copyright 2016 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.
+
+// ignore-tidy-linelength
+
+// error-pattern: cannot declare a new module at this location
+// error-pattern: maybe move this module
+
+mod auxiliary {
+    mod foo;
+}
+
+fn main() {}