diff --git a/changelog.d/13362.misc b/changelog.d/13362.misc
new file mode 100644
index 000000000..c80578ce9
--- /dev/null
+++ b/changelog.d/13362.misc
@@ -0,0 +1 @@
+Add missing type hints to open tracing module.
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index ad5cbf46a..c1aa205ee 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -910,8 +910,8 @@ def tag_args(func: Callable[P, R]) -> Callable[P, R]:
     def _tag_args_inner(*args: P.args, **kwargs: P.kwargs) -> R:
         argspec = inspect.getfullargspec(func)
         for i, arg in enumerate(argspec.args[1:]):
-            set_tag("ARG_" + arg, args[i])  # type: ignore[index]
-        set_tag("args", args[len(argspec.args) :])  # type: ignore[index]
+            set_tag("ARG_" + arg, str(args[i]))  # type: ignore[index]
+        set_tag("args", str(args[len(argspec.args) :]))  # type: ignore[index]
         set_tag("kwargs", str(kwargs))
         return func(*args, **kwargs)