diff --git a/db/javajs.cpp b/db/javajs.cpp
index d318cb7b89b..97f438dc540 100644
--- a/db/javajs.cpp
+++ b/db/javajs.cpp
@@ -578,6 +578,7 @@ JNIEXPORT void JNICALL java_native_say(JNIEnv * env , jclass, jobject outBuffer
     Message in;
 
     jniCallback( out , in );
+    assert( ! out.freeIt );
 }
 
 JNIEXPORT jint JNICALL java_native_call(JNIEnv * env , jclass, jobject outBuffer , jobject inBuffer ) {
@@ -593,6 +594,9 @@ JNIEXPORT jint JNICALL java_native_call(JNIEnv * env , jclass, jobject outBuffer
         JNI_DEBUG( "copying data of len :" << in.data->len );
         assert( env->GetDirectBufferCapacity( inBuffer ) >= in.data->len );
         memcpy( env->GetDirectBufferAddress( inBuffer ) , in.data , in.data->len );
+
+        assert( ! out.freeIt );
+        assert( in.freeIt );
         return in.data->len;
     }