diff --git a/data/themerc.xsd b/data/themerc.xsd
index c1432124..63f8af51 100755
--- a/data/themerc.xsd
+++ b/data/themerc.xsd
@@ -163,5 +163,6 @@
       <xs:element name="window" type="obt:allwindows" minOccurs="0"/>
     </xs:all>
     <xs:attribute name="version" type="xs:integer" use="required" fixed="1"/>
+    <xs:attribute name="engine" type="xs:string" use="required" fixed="box"/>
   </xs:complexType>
 </xs:schema>
diff --git a/parser/parse.c b/parser/parse.c
index 43d076e1..16745650 100644
--- a/parser/parse.c
+++ b/parser/parse.c
@@ -108,20 +108,35 @@ gboolean parse_load_theme(const gchar *name, xmlDocPtr *doc, xmlNodePtr *root,
     GSList *it;
     gchar *path;
     gboolean r = FALSE;
+    gchar *eng;
 
     /* backward compatibility.. */
     path = g_build_filename(g_get_home_dir(), ".themes", name,
                             "openbox-3", "themerc.xml", NULL);
-    if ((r = parse_load(path, "openbox_theme", doc, root)))
-        *retpath = g_path_get_dirname(path);
+    if (parse_load(path, "openbox_theme", doc, root) &&
+        parse_attr_string("engine", *root, &eng))
+    {
+        if (!strcmp(eng, "box")) {
+            *retpath = g_path_get_dirname(path);
+            r = TRUE;
+        }
+        g_free(eng);
+    }
     g_free(path);
 
     if (!r) {
         for (it = xdg_data_dir_paths; !r && it; it = g_slist_next(it)) {
             path = g_build_filename(it->data, "themes", name, "openbox-3",
                                     "themerc.xml", NULL);
-            if ((r = parse_load(path, "openbox_theme", doc, root)))
-                *retpath = g_path_get_dirname(path);
+            if (parse_load(path, "openbox_theme", doc, root) &&
+                parse_attr_string("engine", *root, &eng))
+            {
+                if (!strcmp(eng, "box")) {
+                    *retpath = g_path_get_dirname(path);
+                    r = TRUE;
+                }
+                g_free(eng);
+            }
             g_free(path);
         }
     }
diff --git a/themes/Artwiz-boxed/openbox-3/themerc.xml b/themes/Artwiz-boxed/openbox-3/themerc.xml
index 5ed34474..2bf0cd84 100644
--- a/themes/Artwiz-boxed/openbox-3/themerc.xml
+++ b/themes/Artwiz-boxed/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>4</handle>
     <padding x="1" y="1"/>
diff --git a/themes/Bear2/openbox-3/themerc.xml b/themes/Bear2/openbox-3/themerc.xml
index 3173853e..d5130f01 100644
--- a/themes/Bear2/openbox-3/themerc.xml
+++ b/themes/Bear2/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>4</handle>
     <padding x="3" y="3"/>
diff --git a/themes/Clearlooks-Olive/openbox-3/themerc.xml b/themes/Clearlooks-Olive/openbox-3/themerc.xml
index c57b26ec..c811a1c3 100644
--- a/themes/Clearlooks-Olive/openbox-3/themerc.xml
+++ b/themes/Clearlooks-Olive/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>3</handle>
     <padding x="2" y="2"/>
diff --git a/themes/Clearlooks/openbox-3/themerc.xml b/themes/Clearlooks/openbox-3/themerc.xml
index f4ab5f84..00f45dfa 100644
--- a/themes/Clearlooks/openbox-3/themerc.xml
+++ b/themes/Clearlooks/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>3</handle>
     <padding x="2" y="2"/>
diff --git a/themes/Mikachu/openbox-3/themerc.xml b/themes/Mikachu/openbox-3/themerc.xml
index b1ee489e..6008d4db 100644
--- a/themes/Mikachu/openbox-3/themerc.xml
+++ b/themes/Mikachu/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>0</handle>
     <padding x="1" y="1"/>
diff --git a/themes/Natura/openbox-3/themerc.xml b/themes/Natura/openbox-3/themerc.xml
index 7ce66a80..18841051 100644
--- a/themes/Natura/openbox-3/themerc.xml
+++ b/themes/Natura/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>2</handle>
     <padding x="2" y="2"/>
diff --git a/themes/Orang/openbox-3/themerc.xml b/themes/Orang/openbox-3/themerc.xml
index 5f2e4ff3..f8e3c7b3 100644
--- a/themes/Orang/openbox-3/themerc.xml
+++ b/themes/Orang/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>3</handle>
     <padding x="1" y="1"/>
diff --git a/themes/Syscrash/openbox-3/themerc.xml b/themes/Syscrash/openbox-3/themerc.xml
index 7e7462e9..8931a9c8 100644
--- a/themes/Syscrash/openbox-3/themerc.xml
+++ b/themes/Syscrash/openbox-3/themerc.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<openbox_theme version="1" xmlns="http://openbox.org/themerc">
+<openbox_theme version="1" engine="box" xmlns="http://openbox.org/themerc">
   <dimensions>
     <handle>0</handle>
     <padding x="1" y="1"/>
diff --git a/tools/themetoxml/themetoxml.c b/tools/themetoxml/themetoxml.c
index 12944f88..f7d5aa6e 100644
--- a/tools/themetoxml/themetoxml.c
+++ b/tools/themetoxml/themetoxml.c
@@ -314,6 +314,7 @@ int main(int argc, char **argv)
     doc = xmlNewDoc((const xmlChar*) "1.0");
     xmlDocSetRootElement
         (doc,(root = xmlNewNode(NULL, (const xmlChar*)"openbox_theme")));
+    xmlSetProp(root, (const xmlChar*)"engine", (const xmlChar*)"box");
     xmlSetProp(root, (const xmlChar*)"version", (const xmlChar*)"1");
     xmlSetProp(root, (const xmlChar*)"xmlns",
                (const xmlChar*)"http://openbox.org/themerc");