diff --git a/lib/sparql/client.rb b/lib/sparql/client.rb
index 3ea76642..bc5bc15a 100644
--- a/lib/sparql/client.rb
+++ b/lib/sparql/client.rb
@@ -416,7 +416,7 @@ def cache_invalidate_graph(graphs)
         begin
           graph = graph.to_s
           graph = "sparql:graph:#{graph}" unless graph.start_with?("sparql:graph:")
-          if @redis_cache.exists(graph)
+          if @redis_cache.exists?(graph)
             begin
               @redis_cache.del(graph)
             rescue => exception