diff --git a/scripts/appleseed.package.py b/scripts/appleseed.package.py
index 8596af30c0..308574f421 100755
--- a/scripts/appleseed.package.py
+++ b/scripts/appleseed.package.py
@@ -989,7 +989,7 @@ def get_dependencies_for_file(self, filepath, fix_paths=True, verbose=True):
                         # Try to handle other relative libs.
                         candidate = os.path.join(loader_path, fixed_lib)
                         if not os.path.exists(candidate):
-                            fatal("Unable to resolve lib {}", lib)
+                            fatal("Unable to resolve lib {}".format(lib))
                         lib = candidate
 
                 for path in search_paths: