diff --git a/layout/reftests/line-breaking/reftest.list b/layout/reftests/line-breaking/reftest.list
index d58941a9acb2..e3c0866583c7 100644
--- a/layout/reftests/line-breaking/reftest.list
+++ b/layout/reftests/line-breaking/reftest.list
@@ -30,6 +30,8 @@ random-if(cocoaWidget) == ja-3.html ja-3-ref.html
skip-if(gtkWidget) == quotationmarks-cjk-1.html quotationmarks-cjk-1-ref.html
== smileys-1.html smileys-1-ref.html
== smileys-2.html smileys-2-ref.html
+fails == space-cluster-1.html space-cluster-1-ref.html # bug 1308502
+fails == space-cluster-2.html space-cluster-2-ref.html # bug 1308502
== url-1.html url-1-ref.html
== url-2.html url-2-ref.html
== url-3.html url-3-ref.html
diff --git a/layout/reftests/line-breaking/space-cluster-1-ref.html b/layout/reftests/line-breaking/space-cluster-1-ref.html
new file mode 100644
index 000000000000..73f65d386210
--- /dev/null
+++ b/layout/reftests/line-breaking/space-cluster-1-ref.html
@@ -0,0 +1,4 @@
+
+
+there
should
be
one
word
per
line
+
diff --git a/layout/reftests/line-breaking/space-cluster-1.html b/layout/reftests/line-breaking/space-cluster-1.html
new file mode 100644
index 000000000000..511f7381df38
--- /dev/null
+++ b/layout/reftests/line-breaking/space-cluster-1.html
@@ -0,0 +1,5 @@
+
+
+
+there should be one word͏ per ͏line
+
diff --git a/layout/reftests/line-breaking/space-cluster-2-ref.html b/layout/reftests/line-breaking/space-cluster-2-ref.html
new file mode 100644
index 000000000000..c7fb7ac99e32
--- /dev/null
+++ b/layout/reftests/line-breaking/space-cluster-2-ref.html
@@ -0,0 +1,4 @@
+
+
+Each diacritic should be on a separate line:
+̂
̄
̅
̆
̇
diff --git a/layout/reftests/line-breaking/space-cluster-2.html b/layout/reftests/line-breaking/space-cluster-2.html
new file mode 100644
index 000000000000..a1eb7f9e3f10
--- /dev/null
+++ b/layout/reftests/line-breaking/space-cluster-2.html
@@ -0,0 +1,4 @@
+
+
+Each diacritic should be on a separate line:
+
̂ ̄ ̅ ̆ ̇