diff --git a/wsdef/src/main/java/com/google/gson/webservice/definition/ParamMap.java b/wsdef/src/main/java/com/google/gson/webservice/definition/ParamMap.java
index 7f66cbf3..d4b0c2fe 100644
--- a/wsdef/src/main/java/com/google/gson/webservice/definition/ParamMap.java
+++ b/wsdef/src/main/java/com/google/gson/webservice/definition/ParamMap.java
@@ -41,7 +41,7 @@ class ParamMap {
     }
 
     public Builder<T> put(String paramName, Object content, Type typeOfContent) {
-      spec.checkIfCompatible(paramName, typeOfContent);
+      Preconditions.checkArgument(spec.checkIfCompatible(paramName, typeOfContent));
       contents.put(paramName, content);
       return this;
     }
diff --git a/wsdef/src/main/java/com/google/gson/webservice/definition/RequestBody.java b/wsdef/src/main/java/com/google/gson/webservice/definition/RequestBody.java
index 6afa8ead..593921ca 100644
--- a/wsdef/src/main/java/com/google/gson/webservice/definition/RequestBody.java
+++ b/wsdef/src/main/java/com/google/gson/webservice/definition/RequestBody.java
@@ -23,6 +23,8 @@ import java.util.Map;
  * in the output stream of the request (for example, with 
  * {@link java.net.HttpURLConnection#getOutputStream()}) , and is read by the 
  * {@link javax.servlet.http.HttpServletRequest#getInputStream()}.
+ * This class omits the default constructor for use by Gson. Instead the user must use
+ * {@link com.google.gson.webservice.typeadapters.RequestBodyGsonConverter}
  * 
  * @author inder
  */
diff --git a/wsdef/src/main/java/com/google/gson/webservice/definition/ResponseBody.java b/wsdef/src/main/java/com/google/gson/webservice/definition/ResponseBody.java
index dcc18b81..13b6e17c 100644
--- a/wsdef/src/main/java/com/google/gson/webservice/definition/ResponseBody.java
+++ b/wsdef/src/main/java/com/google/gson/webservice/definition/ResponseBody.java
@@ -20,7 +20,9 @@ import java.util.Map;
 
 /**
  * body of the response. This is written out as JSON to be sent out to the client. 
- * 
+ * This class omits the default constructor for use by Gson. Instead the user must use
+ * {@link com.google.gson.webservice.typeadapters.ResponseBodyGsonConverter}
+ *
  * @author inder
  */
 public final class ResponseBody extends ContentBody {
@@ -46,7 +48,6 @@ public final class ResponseBody extends ContentBody {
     }    
   }
 
-
   private ResponseBody(ResponseBodySpec spec, Map<String, Object> contents) {
     super(spec, contents);
   }