3 files changed, 21 insertions, 8 deletions
diff --git a/cli/js/lib.deno.ns.d.ts b/cli/js/lib.deno.ns.d.ts
index 43e28b05b..bf10049bb 100644
--- a/cli/js/lib.deno.ns.d.ts
+++ b/cli/js/lib.deno.ns.d.ts
@@ -740,7 +740,7 @@ declare namespace Deno {
     recursive?: boolean;
     /** Permissions to use when creating the directory (defaults to `0o777`,
      * before the process's umask).
-     * Does nothing/raises on Windows. */
+     * Ignored on Windows. */
     mode?: number;
   }
 
diff --git a/cli/js/ops/fs/mkdir.ts b/cli/js/ops/fs/mkdir.ts
index 4df33a29f..0bd088def 100644
--- a/cli/js/ops/fs/mkdir.ts
+++ b/cli/js/ops/fs/mkdir.ts
@@ -1,14 +1,16 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { sendSync, sendAsync } from "../dispatch_json.ts";
 
+type MkdirArgs = { path: string; recursive: boolean; mode?: number };
+
 // TODO(ry) The complexity in argument parsing is to support deprecated forms of
 // mkdir and mkdirSync.
 function mkdirArgs(
   path: string,
   optionsOrRecursive?: MkdirOptions | boolean,
   mode?: number
-): { path: string; recursive: boolean; mode: number } {
-  const args = { path, recursive: false, mode: 0o777 };
+): MkdirArgs {
+  const args: MkdirArgs = { path, recursive: false };
   if (typeof optionsOrRecursive == "boolean") {
     args.recursive = optionsOrRecursive;
     if (mode) {
@@ -34,7 +36,7 @@ export interface MkdirOptions {
   recursive?: boolean;
   /** Permissions to use when creating the directory (defaults to `0o777`,
    * before the process's umask).
-   * Does nothing/raises on Windows. */
+   * Ignored on Windows. */
   mode?: number;
 }
 
diff --git a/cli/js/tests/mkdir_test.ts b/cli/js/tests/mkdir_test.ts
index 2921177eb..d1b7aa49b 100644
--- a/cli/js/tests/mkdir_test.ts
+++ b/cli/js/tests/mkdir_test.ts
@@ -15,11 +15,10 @@ unitTest(
   { perms: { read: true, write: true } },
   function mkdirSyncMode(): void {
     const path = Deno.makeTempDirSync() + "/dir";
-    Deno.mkdirSync(path, { mode: 0o755 }); // no perm for x
+    Deno.mkdirSync(path, { mode: 0o737 });
     const pathInfo = Deno.statSync(path);
-    if (pathInfo.mode !== null) {
-      // Skip windows
-      assertEquals(pathInfo.mode & 0o777, 0o755);
+    if (Deno.build.os !== "win") {
+      assertEquals(pathInfo.mode! & 0o777, 0o737 & ~Deno.umask());
     }
   }
 );
@@ -45,6 +44,18 @@ unitTest(
   }
 );
 
+unitTest(
+  { perms: { read: true, write: true } },
+  async function mkdirMode(): Promise<void> {
+    const path = Deno.makeTempDirSync() + "/dir";
+    await Deno.mkdir(path, { mode: 0o737 });
+    const pathInfo = Deno.statSync(path);
+    if (Deno.build.os !== "win") {
+      assertEquals(pathInfo.mode! & 0o777, 0o737 & ~Deno.umask());
+    }
+  }
+);
+
 unitTest({ perms: { write: true } }, function mkdirErrIfExists(): void {
   let err;
   try {