diff --git a/lib/dbSelect.js b/lib/dbSelect.js
index 20823cd..b963458 100644
--- a/lib/dbSelect.js
+++ b/lib/dbSelect.js
@@ -364,7 +364,7 @@ DBSelect.prototype.assemble = DBSelect.prototype.toString = function()
               }
 
               startGroups = 0;
-              sql += whereString;
+              sql += '(' + whereString + ')';
           }
       }