diff --git a/databricks/sdk/mixins/compute.py b/databricks/sdk/mixins/compute.py
index b3b3367d..61733a6f 100644
--- a/databricks/sdk/mixins/compute.py
+++ b/databricks/sdk/mixins/compute.py
@@ -209,31 +209,28 @@ def select_node_type(self,
             return nt.node_type_id
         raise ValueError("cannot determine smallest node type")
 
-    def ensure_cluster_is_running(self, cluster_id: str):
+    def ensure_cluster_is_running(self, cluster_id: str) -> None:
         """Ensures that given cluster is running, regardless of the current state"""
         timeout = datetime.timedelta(minutes=20)
         deadline = time.time() + timeout.total_seconds()
-        cluster_running = False
-        while time.time() < deadline and not cluster_running:
+        while time.time() < deadline:
             try:
                 state = compute.State
                 info = self.get(cluster_id)
                 if info.state == state.RUNNING:
-                    cluster_running = True
+                    return
                 elif info.state == state.TERMINATED:
                     self.start(cluster_id).result()
-                    cluster_running = True
+                    return
                 elif info.state == state.TERMINATING:
                     self.wait_get_cluster_terminated(cluster_id)
                     self.start(cluster_id).result()
-                    cluster_running = True
+                    return
                 elif info.state in (state.PENDING, state.RESIZING, state.RESTARTING):
                     self.wait_get_cluster_running(cluster_id)
-                    cluster_running = True
+                    return
                 elif info.state in (state.ERROR, state.UNKNOWN):
                     raise RuntimeError(f'Cluster {info.cluster_name} is {info.state}: {info.state_message}')
             except OperationFailed as e:
                 _LOG.debug('Operation failed, retrying', exc_info=e)
-
-        if not cluster_running:
-            raise TimeoutError(f'timed out after {timeout}')
+        raise TimeoutError(f'timed out after {timeout}')