diff --git a/lib/java/src/org/apache/thrift/protocol/TSimpleJSONProtocol.java b/lib/java/src/org/apache/thrift/protocol/TSimpleJSONProtocol.java
index 33cad24..e005a4f 100644
--- a/lib/java/src/org/apache/thrift/protocol/TSimpleJSONProtocol.java
+++ b/lib/java/src/org/apache/thrift/protocol/TSimpleJSONProtocol.java
@@ -59,9 +59,17 @@
   private static final TSet EMPTY_SET = new TSet();
   private static final TList EMPTY_LIST = new TList();
   private static final TMap EMPTY_MAP = new TMap();
+  private static final String LIST = "list";
+  private static final String SET = "set";
+  private static final String MAP = "map";
 
   protected class Context {
     protected void write() throws TException {}
+
+    /**
+     * Returns whether the current value is a key in a map
+     */
+    protected boolean isMapKey() { return  false; }
   }
 
   protected class ListContext extends Context {
@@ -91,6 +99,22 @@
     }
   }
 
+  protected class MapContext extends StructContext {
+    protected boolean isKey = true;
+
+    @Override
+    protected void write() throws TException {
+      super.write();
+      isKey = !isKey;
+    }
+
+    protected boolean isMapKey() {
+      // we want to coerce map keys to json strings regardless
+      // of their type
+      return isKey;
+    }
+  }
+
   protected final Context BASE_CONTEXT = new Context();
 
   /**
@@ -119,6 +143,15 @@
   }
 
   /**
+   * Used to make sure that we are not encountering a map whose keys are containers
+   */
+  protected void assertContextIsNotMapKey(String invalidKeyType) throws CollectionMapKeyException {
+    if (writeContext_.isMapKey()) {
+      throw new CollectionMapKeyException("Cannot serialize a map with keys that are of type " + invalidKeyType);
+    }
+  }
+
+  /**
    * Constructor
    */
   public TSimpleJSONProtocol(TTransport trans) {
@@ -159,9 +192,10 @@
   public void writeFieldStop() {}
 
   public void writeMapBegin(TMap map) throws TException {
+    assertContextIsNotMapKey(MAP);
     writeContext_.write();
     trans_.write(LBRACE);
-    pushWriteContext(new StructContext());
+    pushWriteContext(new MapContext());
     // No metadata!
   }
 
@@ -171,6 +205,7 @@
   }
 
   public void writeListBegin(TList list) throws TException {
+    assertContextIsNotMapKey(LIST);
     writeContext_.write();
     trans_.write(LBRACKET);
     pushWriteContext(new ListContext());
@@ -183,6 +218,7 @@
   }
 
   public void writeSetBegin(TSet set) throws TException {
+    assertContextIsNotMapKey(SET);
     writeContext_.write();
     trans_.write(LBRACKET);
     pushWriteContext(new ListContext());
@@ -207,8 +243,12 @@
   }
 
   public void writeI32(int i32) throws TException {
-    writeContext_.write();
-    _writeStringData(Integer.toString(i32));
+    if(writeContext_.isMapKey()) {
+      writeString(Integer.toString(i32));
+    } else {
+      writeContext_.write();
+      _writeStringData(Integer.toString(i32));
+    }
   }
 
   public void _writeStringData(String s) throws TException {
@@ -221,13 +261,21 @@
   }
 
   public void writeI64(long i64) throws TException {
-    writeContext_.write();
-    _writeStringData(Long.toString(i64));
+    if(writeContext_.isMapKey()) {
+      writeString(Long.toString(i64));
+    } else {
+      writeContext_.write();
+      _writeStringData(Long.toString(i64));
+    }
   }
 
   public void writeDouble(double dub) throws TException {
-    writeContext_.write();
-    _writeStringData(Double.toString(dub));
+    if(writeContext_.isMapKey()) {
+      writeString(Double.toString(dub));
+    } else {
+      writeContext_.write();
+      _writeStringData(Double.toString(dub));
+    }
   }
 
   public void writeString(String str) throws TException {
@@ -382,4 +430,9 @@
     return ByteBuffer.wrap(new byte[0]);
   }
 
+  public static class CollectionMapKeyException extends TException {
+    public CollectionMapKeyException(String message) {
+      super(message);
+    }
+  }
 }
diff --git a/lib/java/test/org/apache/thrift/protocol/TestTSimpleJSONProtocol.java b/lib/java/test/org/apache/thrift/protocol/TestTSimpleJSONProtocol.java
new file mode 100644
index 0000000..3bb6a9e
--- /dev/null
+++ b/lib/java/test/org/apache/thrift/protocol/TestTSimpleJSONProtocol.java
@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.thrift.protocol;
+
+import java.io.UnsupportedEncodingException;
+
+import junit.framework.TestCase;
+
+import org.apache.thrift.Fixtures;
+import org.apache.thrift.TException;
+import org.apache.thrift.transport.TMemoryBuffer;
+
+import thrift.test.CompactProtoTestStruct;
+
+public class TestTSimpleJSONProtocol extends TestCase {
+  private TMemoryBuffer buf;
+  private TSimpleJSONProtocol proto;
+
+  @Override
+  protected void setUp() throws Exception {
+    buf = new TMemoryBuffer(1000);
+    proto = new TSimpleJSONProtocol(buf);
+  }
+
+  private String bufToString() {
+    try {
+      return buf.toString("UTF-8");
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  public void testHolyMoley() throws TException {
+    Fixtures.holyMoley.write(proto);
+    assertEquals("{\"big\":[{\"im_true\":1,\"im_false\":0,\"a_bite\":35,\"integer16\":27000,\"integer32\":16777216,\"integer64\":6000000000,\"double_precision\":3.141592653589793,\"some_characters\":\"JSON THIS! \\\"\\u0001\",\"zomg_unicode\":\"ӀⅮΝ Нοⅿоɡгаρℎ Αttαⅽκ�‼\",\"what_who\":0,\"base64\":\"base64\",\"byte_list\":[1,2,3],\"i16_list\":[1,2,3],\"i64_list\":[1,2,3]},{\"im_true\":1,\"im_false\":0,\"a_bite\":-42,\"integer16\":27000,\"integer32\":16777216,\"integer64\":6000000000,\"double_precision\":3.141592653589793,\"some_characters\":\"JSON THIS! \\\"\\u0001\",\"zomg_unicode\":\"ӀⅮΝ Нοⅿоɡгаρℎ Αttαⅽκ�‼\",\"what_who\":0,\"base64\":\"base64\",\"byte_list\":[1,2,3],\"i16_list\":[1,2,3],\"i64_list\":[1,2,3]}],\"contain\":[[],[\"then a one, two\",\"three!\",\"FOUR!!\"],[\"and a one\",\"and a two\"]],\"bonks\":{\"two\":[{\"type\":1,\"message\":\"Wait.\"},{\"type\":2,\"message\":\"What?\"}],\"three\":[],\"zero\":[]}}", bufToString());
+  }
+
+  public void testNesting() throws TException {
+    Fixtures.nesting.write(proto);
+    assertEquals("{\"my_bonk\":{\"type\":31337,\"message\":\"I am a bonk... xor!\"},\"my_ooe\":{\"im_true\":1,\"im_false\":0,\"a_bite\":-42,\"integer16\":27000,\"integer32\":16777216,\"integer64\":6000000000,\"double_precision\":3.141592653589793,\"some_characters\":\"JSON THIS! \\\"\\u0001\",\"zomg_unicode\":\"ӀⅮΝ Нοⅿоɡгаρℎ Αttαⅽκ�‼\",\"what_who\":0,\"base64\":\"base64\",\"byte_list\":[1,2,3],\"i16_list\":[1,2,3],\"i64_list\":[1,2,3]}}", bufToString());
+  }
+
+  public void testOneOfEach() throws TException {
+    Fixtures.oneOfEach.write(proto);
+    assertEquals("{\"im_true\":1,\"im_false\":0,\"a_bite\":-42,\"integer16\":27000,\"integer32\":16777216,\"integer64\":6000000000,\"double_precision\":3.141592653589793,\"some_characters\":\"JSON THIS! \\\"\\u0001\",\"zomg_unicode\":\"ӀⅮΝ Нοⅿоɡгаρℎ Αttαⅽκ�‼\",\"what_who\":0,\"base64\":\"base64\",\"byte_list\":[1,2,3],\"i16_list\":[1,2,3],\"i64_list\":[1,2,3]}", bufToString());
+  }
+
+  public void testSanePartsOfCompactProtoTestStruct() throws TException {
+    // unset all the maps with container keys
+    CompactProtoTestStruct struct = Fixtures.compactProtoTestStruct.deepCopy();
+    struct.unsetList_byte_map();
+    struct.unsetSet_byte_map();
+    struct.unsetMap_byte_map();
+    struct.write(proto);
+    assertEquals("{\"a_byte\":127,\"a_i16\":32000,\"a_i32\":1000000000,\"a_i64\":1099511627775,\"a_double\":5.6789,\"a_string\":\"my string\",\"a_binary\":\"\\u0000\\u0001\\u0002\\u0003\\u0004\\u0005\\u0006\\u0007\\b\",\"true_field\":1,\"false_field\":0,\"empty_struct_field\":{},\"byte_list\":[-127,-1,0,1,127],\"i16_list\":[-1,0,1,32767],\"i32_list\":[-1,0,255,65535,16777215,2147483647],\"i64_list\":[-1,0,255,65535,16777215,4294967295,1099511627775,281474976710655,72057594037927935,9223372036854775807],\"double_list\":[0.1,0.2,0.3],\"string_list\":[\"first\",\"second\",\"third\"],\"boolean_list\":[1,1,1,0,0,0],\"struct_list\":[{},{}],\"byte_set\":[0,1,-127,127,-1],\"i16_set\":[0,1,32767,-1],\"i32_set\":[1,2,3],\"i64_set\":[9223372036854775807,72057594037927935,65535,0,-1,255,1099511627775,281474976710655,4294967295,16777215],\"double_set\":[0.1,0.2,0.3],\"string_set\":[\"second\",\"third\",\"first\"],\"boolean_set\":[0,1],\"struct_set\":[{}],\"byte_byte_map\":{\"1\":2},\"i16_byte_map\":{\"1\":1,\"32767\":1,\"-1\":1},\"i32_byte_map\":{\"1\":1,\"2147483647\":1,\"-1\":1},\"i64_byte_map\":{\"9223372036854775807\":1,\"-1\":1,\"0\":1,\"1\":1},\"double_byte_map\":{\"1.1\":1,\"-1.1\":1},\"string_byte_map\":{\"\":0,\"second\":2,\"third\":3,\"first\":1},\"boolean_byte_map\":{\"0\":0,\"1\":1},\"byte_i16_map\":{\"1\":1,\"2\":-1,\"3\":32767},\"byte_i32_map\":{\"1\":1,\"2\":-1,\"3\":2147483647},\"byte_i64_map\":{\"1\":1,\"2\":-1,\"3\":9223372036854775807},\"byte_double_map\":{\"1\":0.1,\"2\":-0.1,\"3\":1000000.0},\"byte_string_map\":{\"1\":\"\",\"2\":\"blah\",\"3\":\"loooooooooooooong string\"},\"byte_boolean_map\":{\"1\":1,\"2\":0},\"byte_map_map\":{\"0\":{},\"1\":{\"1\":1},\"2\":{\"1\":1,\"2\":2}},\"byte_set_map\":{\"0\":[],\"1\":[1],\"2\":[1,2]},\"byte_list_map\":{\"0\":[],\"1\":[1],\"2\":[1,2]}}", bufToString());
+  }
+
+  public void testThrowsOnCollectionKeys() throws TException {
+    try {
+      Fixtures.compactProtoTestStruct.write(proto);
+      fail("this should throw a CollectionMapKeyException");
+    } catch (TSimpleJSONProtocol.CollectionMapKeyException e) {
+      //
+    }
+  }
+}