diff --git a/src/contrib/gtk-config-store.cc b/src/contrib/gtk-config-store.cc
index 025d47d3e..966900a03 100644
--- a/src/contrib/gtk-config-store.cc
+++ b/src/contrib/gtk-config-store.cc
@@ -304,7 +304,7 @@ cell_tooltip_callback (GtkWidget  *widget,
       }
     break;
   case ModelNode::NODE_ATTRIBUTE: {
-    uint32_t attrIndex;
+    uint32_t attrIndex = 0;
     TypeId tid;
     for (tid = node->object->GetInstanceTypeId (); tid.HasParent (); tid = tid.GetParent ())
       {