diff --git a/include/vlc_plugin.h b/include/vlc_plugin.h
index e90b4772a2..0d5e1561ec 100644
--- a/include/vlc_plugin.h
+++ b/include/vlc_plugin.h
@@ -150,6 +150,10 @@ enum vlc_module_properties
 #define CAT_HIDDEN -1
 #define SUBCAT_HIDDEN -1
 
+/* Unknown/unset/invalid */
+#define CAT_UNKNOWN 0
+#define SUBCAT_UNKNOWN 0
+
 /* Categories and subcategories */
 #define CAT_INTERFACE 1
 #define SUBCAT_INTERFACE_GENERAL 101
diff --git a/modules/gui/macosx/preferences/prefs.m b/modules/gui/macosx/preferences/prefs.m
index fc2cc1be6a..8e2a5f5977 100644
--- a/modules/gui/macosx/preferences/prefs.m
+++ b/modules/gui/macosx/preferences/prefs.m
@@ -488,7 +488,7 @@
         VLCTreeSubCategoryItem * subCategoryItem = nil;
         VLCTreePluginItem * pluginItem = nil;
         module_config_t *p_configs = NULL;
-        int lastsubcat = 0;
+        int lastsubcat = SUBCAT_UNKNOWN;
         unsigned int confsize;
 
         module_t * p_module = modules[i];
diff --git a/modules/gui/qt/dialogs/preferences/complete_preferences.cpp b/modules/gui/qt/dialogs/preferences/complete_preferences.cpp
index 6823413816..d7f339fa71 100644
--- a/modules/gui/qt/dialogs/preferences/complete_preferences.cpp
+++ b/modules/gui/qt/dialogs/preferences/complete_preferences.cpp
@@ -189,7 +189,7 @@ PrefsTree::PrefsTree( qt_intf_t *_p_intf, QWidget *_parent,
         if( module_is_main( p_module) ) continue;
 
         unsigned  confsize;
-        int i_subcategory = 0, i_category = 0;
+        int i_subcategory = SUBCAT_UNKNOWN, i_category = CAT_UNKNOWN;
 
         bool b_options = false;
         module_config_t *const p_config = module_config_get (p_module, &confsize);
@@ -207,14 +207,14 @@ PrefsTree::PrefsTree( qt_intf_t *_p_intf, QWidget *_parent,
             if( CONFIG_ITEM(p_item->i_type) )
                 b_options = true;
 
-            if( b_options && i_category && i_subcategory )
+            if( b_options && i_category != CAT_UNKNOWN && i_subcategory != SUBCAT_UNKNOWN )
                 break;
         }
         module_config_free (p_config);
 
         /* Dummy item, please proceed */
-        if( !b_options || i_category == 0 || i_subcategory == 0 ) continue;
-
+        if( !b_options || i_category == CAT_UNKNOWN || i_subcategory == SUBCAT_UNKNOWN )
+            continue;
 
         // Locate the category item;
         QTreeWidgetItem *subcat_item = NULL;
@@ -495,7 +495,7 @@ bool PrefsItemData::contains( const QString &text, Qt::CaseSensitivity cs )
         return false;
 
     bool is_core = this->i_type != TYPE_MODULE;
-    int id = 0;
+    int id = SUBCAT_UNKNOWN;
 
     /* find our module */
     module_t *p_module;