diff --git a/sabnzbd/api.py b/sabnzbd/api.py
index d05a776..42e88dd 100644
--- a/sabnzbd/api.py
+++ b/sabnzbd/api.py
@@ -1600,7 +1600,7 @@ def build_history(
     # Filter out any items that don't match the search term or category
     if postproc_queue:
         # It would be more efficient to iterate only once, but we accept the penalty for code clarity
-        if isinstance(search, list):
+        if isinstance(categories, list):
             postproc_queue = [nzo for nzo in postproc_queue if nzo.cat in categories]
 
         if isinstance(search, str):