diff --git a/dblayeroo.php b/dblayeroo.php
index 02b2ff9..19a3112 100644
--- a/dblayeroo.php
+++ b/dblayeroo.php
@@ -723,8 +723,8 @@ class dblayeroo
         }
       }
       ksort ($unique);
-      $unique[] = $primary;
-      $unique = array_unique ($unique);
+      if (! in_array ($primary, $unique))
+        $unique[] = $primary;
 
       try
       {
@@ -827,8 +827,8 @@ class dblayeroo
         }
       }
       $unique = array_values ($unique);
-      $unique[] = $primary;
-      $unique = array_unique ($unique);
+      if (! in_array ($primary, $unique))
+        $unique[] = $primary;
       $st = self::$instance[$this->dsn]->prepare ("
             SELECT UPDATE_RULE,DELETE_RULE,COLUMN_NAME,
                    kColUsage.REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME
@@ -939,14 +939,14 @@ class dblayeroo
               array ($unique[$col["constraint_name"]]);
           $unique[$col["constraint_name"]][] = $col["column_name"];
         }
-        else
+        elseif (! in_array ($col["column_name"], $unique))
         {
          $unique[$col["constraint_name"]] = $col["column_name"];
         }
       }
       $unique = array_values ($unique);
-      $unique[] = $primary;
-      $unique = array_unique ($unique);
+      if (! in_array ($primary, $unique))
+        $unique[] = $primary;
       $st = self::$instance[$this->dsn]->prepare ("
         SELECT kColUsage1.column_name COLUMN_NAME,
                kColUsage2.table_name REFERENCED_TABLE_NAME,