diff --git a/js/deno.ts b/js/deno.ts
index 0b6b0fb9b2..ba4a5151e6 100644
--- a/js/deno.ts
+++ b/js/deno.ts
@@ -13,5 +13,6 @@ export {
   lstatSync,
   writeFileSync
 } from "./os";
+export { ErrorKind, DenoError } from "./errors";
 export { libdeno } from "./libdeno";
 export const argv: string[] = [];
diff --git a/js/errors.ts b/js/errors.ts
index ad7b6be21f..d0254ef65f 100644
--- a/js/errors.ts
+++ b/js/errors.ts
@@ -1,10 +1,11 @@
 import * as fbs from "gen/msg_generated";
+export { ErrorKind } from "gen/msg_generated";
 
 // @internal
 export class DenoError<T extends fbs.ErrorKind> extends Error {
   constructor(readonly kind: T, msg: string) {
     super(msg);
-    this.name = `deno.${fbs.ErrorKind[kind]}`;
+    this.name = fbs.ErrorKind[kind];
   }
 }
 
diff --git a/js/fetch_test.ts b/js/fetch_test.ts
index 88cf834bc6..1af3bc2eb7 100644
--- a/js/fetch_test.ts
+++ b/js/fetch_test.ts
@@ -15,7 +15,6 @@ test(async function fetchPerm() {
   } catch (err_) {
     err = err_;
   }
-  // TODO assert(err instanceof deno.PermissionDenied).
-  assert(err);
-  assertEqual(err.name, "deno.PermissionDenied");
+  assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+  assertEqual(err.name, "PermissionDenied");
 });
diff --git a/js/os_test.ts b/js/os_test.ts
index 3c1d926d85..7a252cb737 100644
--- a/js/os_test.ts
+++ b/js/os_test.ts
@@ -16,8 +16,8 @@ test(async function envFailure() {
     const env = deno.env();
   } catch (err) {
     caughtError = true;
-    // TODO assert(err instanceof deno.PermissionDenied).
-    assertEqual(err.name, "deno.PermissionDenied");
+    assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+    assertEqual(err.name, "PermissionDenied");
   }
 
   assert(caughtError);
@@ -47,9 +47,8 @@ test(async function statSyncNotFound() {
     badInfo = deno.statSync("bad_file_name");
   } catch (err) {
     caughtError = true;
-    // TODO assert(err instanceof deno.NotFound).
-    assert(err);
-    assertEqual(err.name, "deno.NotFound");
+    assertEqual(err.kind, deno.ErrorKind.NotFound);
+    assertEqual(err.name, "NotFound");
   }
 
   assert(caughtError);
@@ -78,9 +77,8 @@ test(async function lstatSyncNotFound() {
     badInfo = deno.lstatSync("bad_file_name");
   } catch (err) {
     caughtError = true;
-    // TODO assert(err instanceof deno.NotFound).
-    assert(err);
-    assertEqual(err.name, "deno.NotFound");
+    assertEqual(err.kind, deno.ErrorKind.NotFound);
+    assertEqual(err.name, "NotFound");
   }
 
   assert(caughtError);
@@ -138,8 +136,8 @@ testPerm({ write: true }, function writeFileSyncFail() {
     deno.writeFileSync(filename, data);
   } catch (e) {
     caughtError = true;
-    // TODO assertEqual(e, deno.NotFound);
-    assertEqual(e.name, "deno.NotFound");
+    assertEqual(e.kind, deno.ErrorKind.NotFound);
+    assertEqual(e.name, "NotFound");
   }
   assert(caughtError);
 });
@@ -166,9 +164,8 @@ testPerm({ write: true }, function makeTempDirSync() {
   } catch (err_) {
     err = err_;
   }
-  // TODO assert(err instanceof deno.NotFound).
-  assert(err);
-  assertEqual(err.name, "deno.NotFound");
+  assertEqual(err.kind, deno.ErrorKind.NotFound);
+  assertEqual(err.name, "NotFound");
 });
 
 test(function makeTempDirSyncPerm() {
@@ -179,9 +176,8 @@ test(function makeTempDirSyncPerm() {
   } catch (err_) {
     err = err_;
   }
-  // TODO assert(err instanceof deno.PermissionDenied).
-  assert(err);
-  assertEqual(err.name, "deno.PermissionDenied");
+  assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+  assertEqual(err.name, "PermissionDenied");
 });
 
 testPerm({ write: true }, function mkdirSync() {
@@ -199,9 +195,8 @@ testPerm({ write: false }, function mkdDirSyncPerm() {
   } catch (err_) {
     err = err_;
   }
-  // TODO assert(err instanceof deno.PermissionDenied).
-  assert(err);
-  assertEqual(err.name, "deno.PermissionDenied");
+  assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+  assertEqual(err.name, "PermissionDenied");
 });
 
 testPerm({ write: true }, function renameSync() {
@@ -220,9 +215,8 @@ testPerm({ write: true }, function renameSync() {
     oldPathInfo = deno.statSync(oldpath);
   } catch (err) {
     caughtErr = true;
-    // TODO assert(err instanceof deno.NotFound).
-    assert(err);
-    assertEqual(err.name, "deno.NotFound");
+    assertEqual(err.kind, deno.ErrorKind.NotFound);
+    assertEqual(err.name, "NotFound");
   }
 
   assert(caughtErr);
@@ -238,7 +232,6 @@ test(function renameSyncPerm() {
   } catch (err_) {
     err = err_;
   }
-  // TODO assert(err instanceof deno.PermissionDenied).
-  assert(err);
-  assertEqual(err.name, "deno.PermissionDenied");
+  assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+  assertEqual(err.name, "PermissionDenied");
 });