diff --git a/google-http-client-gson/src/test/java/com/google/api/client/json/gson/GsonGeneratorTest.java b/google-http-client-gson/src/test/java/com/google/api/client/json/gson/GsonGeneratorTest.java
new file mode 100644
index 000000000..caa543836
--- /dev/null
+++ b/google-http-client-gson/src/test/java/com/google/api/client/json/gson/GsonGeneratorTest.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.api.client.json.gson;
+
+import com.google.api.client.json.JsonGenerator;
+import com.google.api.client.test.json.AbstractJsonGeneratorTest;
+import java.io.IOException;
+import java.io.Writer;
+
+public class GsonGeneratorTest extends AbstractJsonGeneratorTest {
+
+  private static final GsonFactory FACTORY = new GsonFactory();
+
+  @Override
+  protected JsonGenerator newGenerator(Writer writer) throws IOException {
+    return FACTORY.createJsonGenerator(writer);
+  }
+}
diff --git a/google-http-client-jackson/src/test/java/com/google/api/client/json/jackson/JacksonGeneratorTest.java b/google-http-client-jackson/src/test/java/com/google/api/client/json/jackson/JacksonGeneratorTest.java
new file mode 100644
index 000000000..bfdfbfe28
--- /dev/null
+++ b/google-http-client-jackson/src/test/java/com/google/api/client/json/jackson/JacksonGeneratorTest.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.api.client.json.jackson;
+
+import com.google.api.client.json.JsonGenerator;
+import com.google.api.client.test.json.AbstractJsonGeneratorTest;
+import java.io.IOException;
+import java.io.Writer;
+
+public class JacksonGeneratorTest extends AbstractJsonGeneratorTest {
+
+  private static final JacksonFactory FACTORY = new JacksonFactory();
+
+  @Override
+  protected JsonGenerator newGenerator(Writer writer) throws IOException {
+    return FACTORY.createJsonGenerator(writer);
+  }
+}
diff --git a/google-http-client-jackson2/src/test/java/com/google/api/client/json/jackson2/JacksonGeneratorTest.java b/google-http-client-jackson2/src/test/java/com/google/api/client/json/jackson2/JacksonGeneratorTest.java
new file mode 100644
index 000000000..4b0af8478
--- /dev/null
+++ b/google-http-client-jackson2/src/test/java/com/google/api/client/json/jackson2/JacksonGeneratorTest.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.api.client.json.jackson2;
+
+import com.google.api.client.json.JsonGenerator;
+import com.google.api.client.test.json.AbstractJsonGeneratorTest;
+import java.io.IOException;
+import java.io.Writer;
+
+public class JacksonGeneratorTest extends AbstractJsonGeneratorTest {
+
+  private static final JacksonFactory FACTORY = new JacksonFactory();
+
+  @Override
+  protected JsonGenerator newGenerator(Writer writer) throws IOException {
+    return FACTORY.createJsonGenerator(writer);
+  }
+}
diff --git a/google-http-client-test/src/main/java/com/google/api/client/test/json/AbstractJsonGeneratorTest.java b/google-http-client-test/src/main/java/com/google/api/client/test/json/AbstractJsonGeneratorTest.java
new file mode 100644
index 000000000..0f92bc10f
--- /dev/null
+++ b/google-http-client-test/src/main/java/com/google/api/client/test/json/AbstractJsonGeneratorTest.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.api.client.test.json;
+
+import com.google.api.client.json.JsonGenerator;
+import java.io.IOException;
+import java.io.StringWriter;
+import java.io.Writer;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import junit.framework.TestCase;
+
+public abstract class AbstractJsonGeneratorTest extends TestCase {
+
+  protected abstract JsonGenerator newGenerator(Writer writer) throws IOException;
+
+  class IterableMap extends HashMap<String, String> implements Iterable<Map.Entry<String, String>> {
+    @Override
+    public Iterator<Map.Entry<String, String>> iterator() {
+      return entrySet().iterator();
+    }
+  }
+
+  public void testSerialize_simpleMap() throws Exception {
+    StringWriter writer = new StringWriter();
+    JsonGenerator generator = newGenerator(writer);
+
+    Map m = new HashMap<String, String>();
+    m.put("a", "b");
+
+    generator.serialize(m);
+    generator.close();
+    assertEquals("{\"a\":\"b\"}", writer.toString());
+  }
+
+  public void testSerialize_iterableMap() throws Exception {
+    StringWriter writer = new StringWriter();
+    JsonGenerator generator = newGenerator(writer);
+
+    Map m = new IterableMap();
+    m.put("a", "b");
+
+    generator.serialize(m);
+    generator.close();
+    assertEquals("{\"a\":\"b\"}", writer.toString());
+  }
+}
diff --git a/google-http-client/src/main/java/com/google/api/client/json/JsonGenerator.java b/google-http-client/src/main/java/com/google/api/client/json/JsonGenerator.java
index b37ac6ced..717a1a58d 100644
--- a/google-http-client/src/main/java/com/google/api/client/json/JsonGenerator.java
+++ b/google-http-client/src/main/java/com/google/api/client/json/JsonGenerator.java
@@ -141,7 +141,8 @@ private void serialize(boolean isJsonString, Object value) throws IOException {
       writeBoolean((Boolean) value);
     } else if (value instanceof DateTime) {
       writeString(((DateTime) value).toStringRfc3339());
-    } else if (value instanceof Iterable<?> || valueClass.isArray()) {
+    } else if ((value instanceof Iterable<?> || valueClass.isArray()) && 
+               !(value instanceof Map<?, ?>) && !(value instanceof GenericData)) {
       writeStartArray();
       for (Object o : Types.iterableOf(value)) {
         serialize(isJsonString, o);