diff --git a/src/buildstream/_cas/cascache.py b/src/buildstream/_cas/cascache.py
index 68fd4b610..61a84b694 100644
--- a/src/buildstream/_cas/cascache.py
+++ b/src/buildstream/_cas/cascache.py
@@ -127,7 +127,13 @@ def contains_directory(self, digest):
         request.fetch_file_blobs = not self._remote_cache
 
         try:
-            local_cas.FetchTree(request)
+            response_future = local_cas.FetchTree.future(request)
+            try:
+                response_future.result()
+            except:
+                response_future.cancel()
+                raise
+
             if not self._remote_cache:
                 return True
         except grpc.RpcError as e:
@@ -141,7 +147,13 @@ def contains_directory(self, digest):
         request = local_cas_pb2.UploadTreeRequest()
         request.root_digest.CopyFrom(digest)
         try:
-            local_cas.UploadTree(request)
+            response_future = local_cas.UploadTree.future(request)
+            try:
+                response_future.result()
+            except:
+                response_future.cancel()
+                raise
+
             return True
         except grpc.RpcError as e:
             if e.code() == grpc.StatusCode.NOT_FOUND:
@@ -231,7 +243,12 @@ def ensure_tree(self, tree):
             request.root_digest.CopyFrom(tree)
             request.fetch_file_blobs = True
 
-            local_cas.FetchTree(request)
+            response_future = local_cas.FetchTree.future(request)
+            try:
+                response_future.result()
+            except:
+                response_future.cancel()
+                raise
 
     # fetch_directory():
     #
@@ -252,7 +269,13 @@ def fetch_directory(self, remote, dir_digest):
         request.fetch_file_blobs = False
 
         try:
-            local_cas.FetchTree(request)
+            response_future = local_cas.FetchTree.future(request)
+            try:
+                response_future.result()
+            except:
+                response_future.cancel()
+                raise
+
         except grpc.RpcError as e:
             if e.code() == grpc.StatusCode.NOT_FOUND:
                 raise BlobNotFound(
@@ -536,7 +559,13 @@ def missing_blobs(self, blobs, *, remote=None):
                 d.CopyFrom(required_digest)
 
             try:
-                response = cas.FindMissingBlobs(request)
+                response_future = cas.FindMissingBlobs.future(request)
+                try:
+                    response = response_future.result()
+                except:
+                    response_future.cancel()
+                    raise
+
             except grpc.RpcError as e:
                 if e.code() == grpc.StatusCode.INVALID_ARGUMENT and e.details().startswith("Invalid instance name"):
                     raise CASCacheError("Unsupported buildbox-casd version: FindMissingBlobs failed") from e
@@ -566,7 +595,12 @@ def required_blobs_for_directory(self, directory_digest, *, excluded_subdirs=Non
             request.root_digest.CopyFrom(directory_digest)
             request.fetch_file_blobs = False
 
-            local_cas.FetchTree(request)
+            response_future = local_cas.FetchTree.future(request)
+            try:
+                response_future.result()
+            except:
+                response_future.cancel()
+                raise
 
         # parse directory, and recursively add blobs
 
diff --git a/src/buildstream/_cas/casremote.py b/src/buildstream/_cas/casremote.py
index 3fefb9d47..f04d8d7be 100644
--- a/src/buildstream/_cas/casremote.py
+++ b/src/buildstream/_cas/casremote.py
@@ -92,7 +92,13 @@ def send(self, *, missing_blobs=None):
         local_cas = self._remote.casd.get_local_cas()
 
         for request in self._requests:
-            batch_response = local_cas.FetchMissingBlobs(request)
+            batch_response_future = local_cas.FetchMissingBlobs.future(request)
+
+            try:
+                batch_response = batch_response_future.result()
+            except:
+                batch_response_future.cancel()
+                raise
 
             for response in batch_response.responses:
                 if response.status.code == code_pb2.NOT_FOUND:
@@ -146,7 +152,13 @@ def send(self):
         local_cas = self._remote.casd.get_local_cas()
 
         for request in self._requests:
-            batch_response = local_cas.UploadMissingBlobs(request)
+            batch_response_future = local_cas.UploadMissingBlobs.future(request)
+
+            try:
+                batch_response = batch_response_future.result()
+            except:
+                batch_response_future.cancel()
+                raise
 
             for response in batch_response.responses:
                 if response.status.code != code_pb2.OK: