diff --git a/openlp/plugins/custom/customplugin.py b/openlp/plugins/custom/customplugin.py
index 7f64aab52..362f8d64c 100644
--- a/openlp/plugins/custom/customplugin.py
+++ b/openlp/plugins/custom/customplugin.py
@@ -78,7 +78,7 @@ class CustomPlugin(Plugin):
         return about_text
 
     def can_delete_theme(self, theme):
-        filter_string = u'theme_name=%s' % theme
+        filter_string = u'theme_name=\'%s\'' % theme
         if not self.custommanager.get_all_objects_filtered(CustomSlide,
             filter_string):
             return True
diff --git a/openlp/plugins/songs/songsplugin.py b/openlp/plugins/songs/songsplugin.py
index d128bc6a2..c24352a91 100644
--- a/openlp/plugins/songs/songsplugin.py
+++ b/openlp/plugins/songs/songsplugin.py
@@ -199,7 +199,7 @@ class SongsPlugin(Plugin):
         return about_text
 
     def can_delete_theme(self, theme):
-        filter_string = u'theme_name=%s' % theme
+        filter_string = u'theme_name=\'%s\'' % theme
         if not self.manager.get_all_objects_filtered(Song, filter_string):
             return True
         return False