diff --git a/goodconf/__init__.py b/goodconf/__init__.py
index 66f743d..ef7586b 100644
--- a/goodconf/__init__.py
+++ b/goodconf/__init__.py
@@ -260,7 +260,7 @@ def generate_markdown(cls) -> str:
         for k, v in cls.__fields__.items():
             lines.append(f"* **{k}**")
             if v.required:
-                lines[-1] = lines[-1] + " _REQUIRED_"
+                lines[-1] = f"{lines[-1]} _REQUIRED_"
             if v.field_info.description:
                 lines.append(f"  * description: {v.field_info.description}")
             lines.append(f"  * type: `{type_to_str(v.outer_type_)}`")