diff --git a/gcloud-java-datastore/src/main/java/com/google/gcloud/spi/DefaultDatastoreRpc.java b/gcloud-java-datastore/src/main/java/com/google/gcloud/spi/DefaultDatastoreRpc.java
index 2f245260b325..e20bd9a3f9d6 100644
--- a/gcloud-java-datastore/src/main/java/com/google/gcloud/spi/DefaultDatastoreRpc.java
+++ b/gcloud-java-datastore/src/main/java/com/google/gcloud/spi/DefaultDatastoreRpc.java
@@ -32,6 +32,7 @@
 import com.google.api.services.datastore.client.DatastoreException;
 import com.google.api.services.datastore.client.DatastoreFactory;
 import com.google.api.services.datastore.client.DatastoreOptions.Builder;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
 import com.google.gcloud.datastore.DatastoreOptions;
 import com.google.gcloud.spi.DatastoreRpc.DatastoreRpcException.Reason;
@@ -40,6 +41,10 @@
 import org.json.JSONObject;
 import org.json.JSONTokener;
 
+import java.net.InetAddress;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.UnknownHostException;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -62,14 +67,45 @@ public class DefaultDatastoreRpc implements DatastoreRpc {
   }
 
   public DefaultDatastoreRpc(DatastoreOptions options) {
+    String normalizedHost = normalizeHost(options.host());
     client = DatastoreFactory.get().create(
         new Builder()
             .dataset(options.projectId())
-            .host(options.host())
+            .host(normalizedHost)
             .initializer(options.httpRequestInitializer())
             .build());
   }
 
+  private static String normalizeHost(String host) {
+    host = host.toLowerCase();
+    if (includesScheme(host)) {
+      Preconditions.checkArgument(!(host.startsWith("https://") && isLocalHost(host)), 
+          "\"https\" is not supported for localhost.  Use \"http\" instead.");
+      return host;
+    }
+    return "http://" + host;
+  }
+
+  private static boolean isLocalHost(String host) {
+    if (host != null) {
+      try {
+        String normalizedHost = host;
+        if (!includesScheme(normalizedHost)) {
+          normalizedHost = "http://" + normalizedHost;
+        }
+        InetAddress hostAddr = InetAddress.getByName(new URL(normalizedHost).getHost());
+        return hostAddr.isAnyLocalAddress() || hostAddr.isLoopbackAddress();
+      } catch (UnknownHostException | MalformedURLException e) {
+        // ignore
+      }
+    }
+    return false;
+  }
+
+  private static boolean includesScheme(String url) {
+    return url.startsWith("http://") || url.startsWith("https://");
+  }
+
   private static DatastoreRpcException translate(DatastoreException exception) {
     String message = exception.getMessage();
     String reasonStr = "";