diff --git a/lib/dbwrap.js b/lib/dbwrap.js
index cc67861..3e09731 100644
--- a/lib/dbwrap.js
+++ b/lib/dbwrap.js
@@ -13,7 +13,12 @@ function wrap(db, dir, dbsMap) {
   }
 
   db.escape = function (str) {
-    return (str||'').toString().replace(/'/g, "''");
+    // TODO? literals for true,false,null
+    // error on undefined?
+    if (undefined === str) {
+      str = '';
+    }
+    return String(str).replace(/'/g, "''");
   };
 
   function lowerFirst(str) {
@@ -233,10 +238,13 @@ function wrap(db, dir, dbsMap) {
             sql += 'AND ';
           }
           if (null === obj[key]) {
-            sql += db.escape(snakeCase(key)) + " IS '" + db.escape(obj[key]) + "'";
+            sql += db.escape(snakeCase(key)) + " IS null";
           }
           else {
-            sql += db.escape(snakeCase(key)) + " = '" + db.escape(obj[key]) + "'";
+            // TODO check that key is some type? ignore undefined?
+            if (undefined === obj[key]) {
+              sql += db.escape(snakeCase(key)) + " = '" + db.escape(obj[key]) + "'";
+            }
           }
         });
       }