diff --git a/src/access_py_telemetry/api.py b/src/access_py_telemetry/api.py
index 679cca1..157023d 100644
--- a/src/access_py_telemetry/api.py
+++ b/src/access_py_telemetry/api.py
@@ -108,7 +108,9 @@ def request_timeout(self, timeout: float | None) -> None:
         if timeout is None:
             self._request_timeout = None
             return None
-        elif timeout <= 0:
+        if not isinstance(timeout, (int, float)):
+            raise TypeError("Timeout must be a number")
+        elif timeout <= 0 or not isinstance(timeout, (int, float)):
             raise ValueError("Timeout must be a positive number")
 
         self._request_timeout = timeout
diff --git a/tests/test_api.py b/tests/test_api.py
index 27377ac..5f65fe1 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -261,5 +261,23 @@ def test_api_handler_invalid_endpoint(api_handler):
 
     assert "Endpoint for 'payu' not found " in str(excinfo.value)
 
-    ApiHandler._instance = None
-    api_handler._instance = None
+
+def test_api_handler_set_timeout(api_handler):
+    """
+    Make sure that we can set the timeout for the APIHandler class, and that it
+    is either a positive float or None.
+    """
+
+    with pytest.raises(ValueError):
+        api_handler.request_timeout = -1
+
+    with pytest.raises(TypeError):
+        api_handler.request_timeout = "string"
+
+    api_handler.request_timeout = 1.0
+
+    assert api_handler.request_timeout == 1.0
+
+    api_handler.request_timeout = None
+
+    assert api_handler.request_timeout is None