diff --git a/tests/parallel.sh b/tests/parallel.sh
index 946e0a103b..565c6f735a 100644
--- a/tests/parallel.sh
+++ b/tests/parallel.sh
@@ -27,7 +27,7 @@ clearStore
 
 rm -f $SHARED.cur $SHARED.max
 
-drvPath=$($nixinstantiate parallel.nix --argstr sleepTime 8)
+drvPath=$($nixinstantiate parallel.nix --argstr sleepTime 15)
 
 cmd="$nixstore -j1 -r $drvPath"