diff --git a/qutebrowser/models/completion.py b/qutebrowser/models/completion.py
index ffc3a83b7..8630e0c1e 100644
--- a/qutebrowser/models/completion.py
+++ b/qutebrowser/models/completion.py
@@ -210,10 +210,13 @@ class QuickmarkCompletionModel(basecompletion.BaseCompletionModel):
             for qm_name, qm_url in objreg.get('quickmark-manager').marks.items():
                 qmlist.append((qm_url, qm_name))
 
-        if match_field == 'name':
+        elif match_field == 'name':
             for qm_name, qm_url in objreg.get('quickmark-manager').marks.items():
                 qmlist.append((qm_name, qm_url))
 
+        else:
+            raise ValueError("Invalid value '{}' for match_field!".format(match_field))
+
         cat = self.new_category("Quickmarks")
         for (name, desc) in qmlist:
             self.new_item(cat, name, desc)