diff --git a/db/btree.cpp b/db/btree.cpp
index 5279a4d43f5..ab70a03d360 100644
--- a/db/btree.cpp
+++ b/db/btree.cpp
@@ -288,7 +288,7 @@ namespace mongo {
      */
     template< class V >
     inline int BucketBasics<V>::_alloc(int bytes) {
-        dassert( this->emptySize > bytes );
+        assert( this->emptySize >= bytes );
         this->topSize += bytes;
         this->emptySize -= bytes;
         int ofs = totalDataSize() - this->topSize;