diff --git a/tools/build/build.py b/tools/build/build.py
index 3163b67b..dd025173 100755
--- a/tools/build/build.py
+++ b/tools/build/build.py
@@ -226,7 +226,15 @@ def filter_source(tarinfo):
     name = tarinfo.name
     if re.search('^[._]', name) or re.search('/[._]', name) or re.search('~$', name):
         return None
-    if re.search('^OxJS/(downloads|tools/geo/png/icons)', name):
+    if re.search('^OxJS/downloads', name):
+        return None
+    if name == 'OxJS/tools/geo/png/icons.png':
+        return None
+    if re.search('^OxJS/tools/geo/png/icons/', name) and (
+        not re.search('4096', name) or not os.path.exists(
+            name.replace('OxJS/', '../../').replace('icons/4096', 'flags')
+        )
+    ):
         return None
     return tarinfo