diff --git a/graphql_client_codegen/src/lib.rs b/graphql_client_codegen/src/lib.rs
index dcc79426..e21adee2 100644
--- a/graphql_client_codegen/src/lib.rs
+++ b/graphql_client_codegen/src/lib.rs
@@ -80,8 +80,8 @@ fn get_set_schema_from_file(schema_path: &std::path::Path) -> Schema {
     get_set_cached(&SCHEMA_CACHE, schema_path, move || {
         let schema_extension = schema_path
             .extension()
-            .and_then(std::ffi::OsStr::to_str)
-            .unwrap_or("INVALID");
+            .map(|ext| ext.to_str().expect("Path must be valid UTF-8"))
+            .unwrap_or("<no extension>");
         let schema_string = read_file(schema_path).unwrap();
         match schema_extension {
             "graphql" | "gql" => {