diff --git a/content/base/test/Makefile.in b/content/base/test/Makefile.in
index 87785aed1879..598e73532aca 100644
--- a/content/base/test/Makefile.in
+++ b/content/base/test/Makefile.in
@@ -62,7 +62,9 @@ XPCSHELL_TESTS = \
 
 include $(topsrcdir)/config/rules.mk
 
-_TEST_FILES = 	test_bug5141.html \
+# Split files arbitrarily in two groups to not run into too-long command lines
+# which break on Windows (see bug 563151)
+_TEST_FILES1 = 	test_bug5141.html \
 		test_bug51034.html \
 		test_bug166235.html \
 		test_bug199959.html \
@@ -263,6 +265,9 @@ _TEST_FILES = 	test_bug5141.html \
 		file_XHRDocURI.xml^headers^ \
 		file_XHRDocURI.text \
 		file_XHRDocURI.text^headers^ \
+		$(NULL)
+
+_TEST_FILES2 = \
 		test_bug459424.html \
 		bug461735-redirect1.sjs \
 		bug461735-redirect2.sjs \
@@ -387,7 +392,7 @@ _TEST_FILES = 	test_bug5141.html \
 
 # This test fails on the Mac for some reason
 ifneq (,$(filter gtk2 windows,$(MOZ_WIDGET_TOOLKIT)))
-_TEST_FILES += 	test_copyimage.html \
+_TEST_FILES2 += 	test_copyimage.html \
 		$(NULL)
 endif
 
@@ -402,5 +407,8 @@ endif
 #		test_bug503473.html \
 #		file_bug503473-frame.sjs \
 
-libs:: $(_TEST_FILES)
+libs:: $(_TEST_FILES1)
+	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)
+
+libs:: $(_TEST_FILES2)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)