diff --git a/tools/run-mypy b/tools/run-mypy
index 3f7e3b7380..6366d883fa 100755
--- a/tools/run-mypy
+++ b/tools/run-mypy
@@ -42,7 +42,6 @@ exclude_py2 = []
 exclude_py3 = """
 zerver/lib/actions.py
 zerver/lib/ccache.py
-zerver/lib/debug.py
 zerver/lib/email_mirror.py
 zerver/lib/notifications.py
 zerver/lib/tornado_ioloop_logging.py
diff --git a/zerver/lib/debug.py b/zerver/lib/debug.py
index a88aae5434..44f235f7e3 100644
--- a/zerver/lib/debug.py
+++ b/zerver/lib/debug.py
@@ -30,5 +30,5 @@ def interactive_debug(sig, frame):
 # SIGUSR2 => Print stack + open interactive debugging shell
 def interactive_debug_listen():
     # type: () -> None
-    signal.signal(signal.SIGUSR1, lambda sig, stack: traceback.print_stack(stack))
+    signal.signal(signal.SIGUSR1, lambda sig, stack: traceback.print_stack(stack)) # type: ignore # https://github.com/python/typeshed/issues/294
     signal.signal(signal.SIGUSR2, interactive_debug)