diff --git a/testmodule/providers/jsonrpc/rpc_mock.nim b/testmodule/providers/jsonrpc/rpc_mock.nim
index 57cf6a8..d9cae74 100644
--- a/testmodule/providers/jsonrpc/rpc_mock.nim
+++ b/testmodule/providers/jsonrpc/rpc_mock.nim
@@ -36,7 +36,7 @@ proc start*(server: MockRpcHttpServer) =
     if(not hasKey(server.filters, id)):
       raise (ref ApplicationError)(code: -32000, msg: "filter not found")
 
-    del(server.filters, id)
+    server.filters.del(id)
     return true
 
   server.srv.start()
diff --git a/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim b/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim
index 003490d..f9cae91 100644
--- a/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim
+++ b/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim
@@ -142,7 +142,10 @@ suite "HTTP polling subscriptions - filter not found":
 
     await sleepAsync(300.millis)
     mockServer.invalidateFilter(id)
-    await sleepAsync(300.millis)
-    check mockServer.newFilterCounter == 2
+    check eventually mockServer.newFilterCounter == 2
+    check mockServer.filters[id] == false
+    check mockServer.filters.len() == 2
     await subscriptions.unsubscribe(jsonId)
+    check mockServer.filters.len() == 1
+