diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 6645d6f90ff..9adffb526f0 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1172,7 +1172,7 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "emit noalias metadata for mutable references"),
     dump_mir: Option<String> = (None, parse_opt_string, [UNTRACKED],
           "dump MIR state at various points in translation"),
-    dump_mir_dir: Option<String> = (Some(String::from("mir_dump")), parse_opt_string, [UNTRACKED],
+    dump_mir_dir: String = (String::from("mir_dump"), parse_string, [UNTRACKED],
           "the directory the MIR is dumped into"),
     dump_mir_graphviz: bool = (false, parse_bool, [UNTRACKED],
           "in addition to `.mir` files, create graphviz `.dot` files"),
diff --git a/src/librustc_mir/util/liveness.rs b/src/librustc_mir/util/liveness.rs
index 765d50b4006..6251b64bb27 100644
--- a/src/librustc_mir/util/liveness.rs
+++ b/src/librustc_mir/util/liveness.rs
@@ -407,10 +407,7 @@ fn dump_matched_mir_node<'a, 'tcx>(
     result: &LivenessResult,
 ) {
     let mut file_path = PathBuf::new();
-    if let Some(ref file_dir) = tcx.sess.opts.debugging_opts.dump_mir_dir {
-        let p = Path::new(file_dir);
-        file_path.push(p);
-    };
+    file_path.push(Path::new(&tcx.sess.opts.debugging_opts.dump_mir_dir));
     let item_id = tcx.hir.as_local_node_id(source.def_id).unwrap();
     let file_name = format!("rustc.node{}{}-liveness.mir", item_id, pass_name);
     file_path.push(&file_name);
diff --git a/src/librustc_mir/util/pretty.rs b/src/librustc_mir/util/pretty.rs
index 37f59773cd6..78d55ad34ed 100644
--- a/src/librustc_mir/util/pretty.rs
+++ b/src/librustc_mir/util/pretty.rs
@@ -189,11 +189,7 @@ fn dump_path(
     };
 
     let mut file_path = PathBuf::new();
-
-    if let Some(ref file_dir) = tcx.sess.opts.debugging_opts.dump_mir_dir {
-        let p = Path::new(file_dir);
-        file_path.push(p);
-    };
+    file_path.push(Path::new(&tcx.sess.opts.debugging_opts.dump_mir_dir));
 
     let item_name = tcx.hir
         .def_path(source.def_id)