diff --git a/setup.cfg b/setup.cfg
index 8abf358..54e44eb 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -34,6 +34,8 @@ dev =
     flake8==3.9.2
     flake8-builtins==1.5.3  # For disallowing shadowing of Python built-ins.
     flake8-import-order==0.18.1
+    # For Python 3.7 compatibility.
+    importlib-metadata<5
     # Typing related.
     mypy
     # Formatting.