diff --git a/tests/gc-auto.sh b/tests/gc-auto.sh
index 5c8be7c0e..87f1d6798 100644
--- a/tests/gc-auto.sh
+++ b/tests/gc-auto.sh
@@ -23,10 +23,13 @@ with import ./config.nix; mkDerivation {
     echo foo > \$out/bar
     echo 1...
     sleep 2
-    echo 200 > $fake_free
+    echo 200 > ${fake_free}.tmp1
+    mv ${fake_free}.tmp1 $fake_free
     echo 2...
-    sleep 2
+    sleep 1
     echo 3...
+    sleep 1
+    echo 4...
     [[ \$(ls \$NIX_STORE/*-garbage? | wc -l) = 1 ]]
   '';
 }
@@ -42,10 +45,13 @@ with import ./config.nix; mkDerivation {
     echo foo > \$out/bar
     echo 1...
     sleep 2
-    echo 200 > $fake_free
+    echo 200 > ${fake_free}.tmp2
+    mv ${fake_free}.tmp2 $fake_free
     echo 2...
-    sleep 2
+    sleep 1
     echo 3...
+    sleep 1
+    echo 4...
   '';
 }
 EOF