diff --git a/js/src/devtools/automation/cgc-jstests-slow.txt b/js/src/devtools/automation/cgc-jstests-slow.txt
index aa09bdcea173..2cb69816c7d0 100644
--- a/js/src/devtools/automation/cgc-jstests-slow.txt
+++ b/js/src/devtools/automation/cgc-jstests-slow.txt
@@ -48,6 +48,7 @@ ecma_6/String/normalize-generateddata-part1.js
 ecma_6/String/normalize-generateddata-part2.js
 ecma_6/String/normalize-generateddata-part3.js
 js1_5/GC/regress-203278-2.js
+js1_5/GC/regress-203278-3.js
 js1_5/GC/regress-278725.js
 js1_5/Regress/regress-360969-01.js
 js1_5/Regress/regress-360969-02.js