diff --git a/src/spikeinterface/comparison/groundtruthstudy.py b/src/spikeinterface/comparison/groundtruthstudy.py
index adc2898071..23d13c0afe 100644
--- a/src/spikeinterface/comparison/groundtruthstudy.py
+++ b/src/spikeinterface/comparison/groundtruthstudy.py
@@ -21,7 +21,7 @@
 
 
 # This is to separate names when the key are tuples when saving folders
-_key_separator = "--"
+_key_separator = "_##_"
 
 
 class GroundTruthStudy: