diff --git a/generic_rag/graphs/ret_gen.py b/generic_rag/graphs/ret_gen.py
index 9cb69bb..9a05349 100644
--- a/generic_rag/graphs/ret_gen.py
+++ b/generic_rag/graphs/ret_gen.py
@@ -61,12 +61,11 @@ class RetGenLangGraph:
             return pdf_sources
 
         for doc in self.last_retrieved_docs:
-            try:
-                Path(doc.metadata["source"]).suffix == ".pdf"
-            except KeyError:
-                continue
-            else:
+            source_candidate = doc.metadata["source"]
+            if "source" in doc.metadata and Path(doc.metadata["source"]).suffix.lower() == ".pdf":
                 source = doc.metadata["source"]
+            else:
+                continue
 
             if source not in pdf_sources:
                 pdf_sources[source] = set()