diff --git a/dblayeroo.php b/dblayeroo.php
index e929a29..27069f3 100644
--- a/dblayeroo.php
+++ b/dblayeroo.php
@@ -2184,10 +2184,11 @@ class dblayeroo
     // - Check the unique entries (if defined)
     // The primary key is always unique : add it if not set by the user
     $this->debugLog ("    verify the unique constraint");
-    if (! in_array ($this->primary, $this->unique))
-      $uniques = array_merge (array ($this->primary), $this->unique);
-    else
-      $uniques = $this->unique;
+    $uniques = $this->unique;
+    if (! is_array ($uniques))
+      $uniques = array ();
+    if (! in_array ($this->primary, $uniques))
+      $uniques = array_merge (array ($this->primary), $uniques);
     $setValues = $values;
     if (! array_key_exists ($this->primary, $setValues))
       $setValues[$this->primary] = null;