diff --git a/compdb/postprocess.py b/compdb/postprocess.py
index 67d5a60..90e60e5 100755
--- a/compdb/postprocess.py
+++ b/compdb/postprocess.py
@@ -72,7 +72,7 @@
     print("Preparing compilation database...")
 
     db_entries = []
-    for db in compile_command_json_db_files:
+    for db in set(compile_command_json_db_files):
             with open(db, 'r') as f:
                 db_entries.extend(json.load(f))