diff --git a/src/Package.zig b/src/Package.zig
index 532439c60c2b1062a44c61a8a21befaf6da37986..e8431927b1108d51ce1964b81e00a553259da4e1 100644
--- a/src/Package.zig
+++ b/src/Package.zig
@@ -582,6 +582,7 @@ fn fetchAndUnpack(
     });
 
     const mod = try createWithDir(gpa, global_cache_directory, pkg_dir_sub_path, build_zig_basename);
+    try all_modules.put(gpa, actual_hex, mod);
     return .{
         .mod = mod,
         .found_existing = false,