diff --git a/ipwb/indexer.py b/ipwb/indexer.py
index 66d7cd94..ecb904be 100755
--- a/ipwb/indexer.py
+++ b/ipwb/indexer.py
@@ -128,13 +128,13 @@ def index_file_at(warc_paths, encryption_key=None,
     warc_paths_to_remove = []
     for warc_path in warc_paths:
         if is_wacz(warc_path):
-            warc_paths_to_append.append(
-                extract_warcs_from_wacz(warc_path))
+            warc_paths_to_append += extract_warcs_from_wacz(warc_path)
             warc_paths_to_remove.append(warc_path)
 
     # Manipulate list of WARCs extracted from WACZ
-    warc_paths.remove(warc_paths_to_remove)
-    warc_paths += warc_paths_to_append
+    for ptr in warc_paths_to_remove:
+        warc_paths.remove(ptr)
+    warc_paths = warc_paths + warc_paths_to_append
 
     cdxj_lines = []
 
diff --git a/ipwb/util.py b/ipwb/util.py
index b52cad9a..98c0f7bf 100644
--- a/ipwb/util.py
+++ b/ipwb/util.py
@@ -354,14 +354,14 @@ def get_warc_paths_in_wacz(wacz_path):
         return [w for w in z.namelist() if w.startswith('archive/')]
 
 
-def extract_warcs_to_disk(warc_paths):
+def extract_warcs_to_disk(wacz_path, warc_paths):
     for warc in warc_paths:
-        with ZipFile(warc) as z:
+        with ZipFile(wacz_path) as z:
             z.extract(warc)
 
 
 def extract_warcs_from_wacz(wacz_path):
     warc_paths = get_warc_paths_in_wacz(wacz_path)
-    extract_warcs_to_disk(warc_paths)
+    extract_warcs_to_disk(wacz_path, warc_paths)
 
     return glob.glob('archive/*')