diff --git a/engine/core/script/dart_controller.cc b/engine/core/script/dart_controller.cc
index d024c441529794f94be1877265f11337e9cac589..04b03c117f329dbea5da92a91cdc32868e24a421 100644
--- a/engine/core/script/dart_controller.cc
+++ b/engine/core/script/dart_controller.cc
@@ -119,7 +119,9 @@ void DartController::DidLoadMainLibrary(KURL url) {
 
   Dart_Handle library = Dart_LookupLibrary(
       StringToDart(dart_state(), url.string()));
-  CHECK(!LogIfError(library));
+  // TODO(eseidel): We need to load a 404 page instead!
+  if (LogIfError(library))
+    return;
   DartInvokeAppField(library, ToDart("main"), 0, nullptr);
 }
 
diff --git a/engine/core/script/dart_loader.cc b/engine/core/script/dart_loader.cc
index 773637a59789831f3d890e495baa385abf130375..f6efdb363dcf6bdc1cba3eba81363fe0d569fbe9 100644
--- a/engine/core/script/dart_loader.cc
+++ b/engine/core/script/dart_loader.cc
@@ -239,6 +239,11 @@ void DartLoader::WaitForDependencies(
 }
 
 void DartLoader::LoadLibrary(const KURL& url, mojo::URLResponsePtr response) {
+  if (response && response->status_code >= 400) {
+    LOG(ERROR) << url.string().utf8().data()
+        << " failed with " << response->status_code;
+  }
+
   const auto& result = pending_libraries_.add(url.string(), nullptr);
   if (result.isNewEntry) {
     OwnPtr<Job> job = adoptPtr(new ImportJob(this, url));
diff --git a/services/oknet/src/org/domokit/oknet/UrlLoaderImpl.java b/services/oknet/src/org/domokit/oknet/UrlLoaderImpl.java
index 5a23cc1f249bbda907665bdb8df26ab323c7de97..80340511ac7b2a71228d9107ccfdf2f4d304bec2 100644
--- a/services/oknet/src/org/domokit/oknet/UrlLoaderImpl.java
+++ b/services/oknet/src/org/domokit/oknet/UrlLoaderImpl.java
@@ -76,9 +76,14 @@ public class UrlLoaderImpl implements UrlLoader {
                     buffer.put(tmp);
                     mProducer.endWriteData(result == -1 ? 0 : result);
                 } catch (MojoException e) {
-                    if (e.getMojoResult() != MojoResult.SHOULD_WAIT)
+                    // No one read the pipe, they just closed it.
+                    if (e.getMojoResult() == MojoResult.FAILED_PRECONDITION) {
+                        break;
+                    } else if (e.getMojoResult() == MojoResult.SHOULD_WAIT) {
+                        mCore.wait(mProducer, Core.HandleSignals.WRITABLE, -1);
+                    } else {
                         throw e;
-                    mCore.wait(mProducer, Core.HandleSignals.WRITABLE, -1);
+                    }
                 } catch (IOException e) {
                     Log.e(TAG, "mSource.read failed", e);
                     break;