diff --git a/browser/components/sessionstore/test/browser/Makefile.in b/browser/components/sessionstore/test/browser/Makefile.in
index 9bb1825051e..d2d66b75622 100644
--- a/browser/components/sessionstore/test/browser/Makefile.in
+++ b/browser/components/sessionstore/test/browser/Makefile.in
@@ -45,6 +45,7 @@ include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
 # browser_477657.js is disabled, because it's unreliable (bug 482975).
+# browser_480148.js is disabled, because it breaks browser_420786.js (see bug 483382).
 
 _BROWSER_TEST_FILES = \
 	browser_248970_a.js \
@@ -76,7 +77,6 @@ _BROWSER_TEST_FILES = \
 	browser_466937_sample.html \
 	browser_476161.js \
 	browser_476161_sample.html \
-	browser_480148.js \
 	$(NULL)
 
 libs:: $(_BROWSER_TEST_FILES)
diff --git a/browser/components/shell/test/browser_420786.js b/browser/components/shell/test/browser_420786.js
index b38facc44e7..93e7aba4e81 100644
--- a/browser/components/shell/test/browser_420786.js
+++ b/browser/components/shell/test/browser_420786.js
@@ -80,10 +80,6 @@ function onPageLoad() {
 }
 
 function test() {
-  // XXX test disabled, see bug 483382.
-  finish();
-  return;
-
   var osString = Cc["@mozilla.org/xre/app-info;1"].
                  getService(Ci.nsIXULRuntime).OS;