Forgot to add special whereCondition fix for postgres as well.

lib/dialects/postgres/query-generator.js

@@ -483,18 +483,26 @@ module.exports = (function() {
       })
     },
 
-    getWhereConditions: function(smth, tableName) {
+    getWhereConditions: function(smth, tableName, factory) {
       var result = null
+        , where = {}
 
       if (Utils.isHash(smth)) {
         smth = Utils.prependTableNameToHash(tableName, smth)
         result = this.hashToWhereConditions(smth)
-      }
-      else if (typeof smth === "number") {
-        smth = Utils.prependTableNameToHash(tableName, { id: smth })
+      } else if (typeof smth === 'number') {
+        var primaryKeys = !!factory ? Object.keys(factory.primaryKeys) : []
+        if (primaryKeys.length > 0) {
+          // Since we're just a number, assume only the first key
+          primaryKeys = primaryKeys[0]
+        } else {
+          primaryKeys = 'id'
+        }
+
+        where[primaryKeys] = smth
+        smth   = Utils.prependTableNameToHash(tableName, where)
         result = this.hashToWhereConditions(smth)
-      }
-      else if (typeof smth === "string") {
+      } else if (typeof smth === "string") {
         result = smth
       }
       else if (Array.isArray(smth)) {