diff --git a/layout/reftests/bugs/621918-2-ref.svg b/layout/reftests/bugs/621918-2-ref.svg
index 1cf1715fdce..eb789dd4830 100644
--- a/layout/reftests/bugs/621918-2-ref.svg
+++ b/layout/reftests/bugs/621918-2-ref.svg
@@ -3,6 +3,10 @@
    xmlns:xlink="http://www.w3.org/1999/xlink"
    height="800px"
    width="800px">
+
+ <!-- use an empty g to force filters.svg to load before onload -->
+ <use xlink:href="../filters.svg#empty" />
+
  <g filter="url(../filters.svg#NonWhiteToBlack)">
   <rect x="0" y="0" height="100%" width="100%" fill="#FFFFFF"/>
   <text style="font-size:12px;" transform="translate(40,100)">
diff --git a/layout/reftests/bugs/621918-2.svg b/layout/reftests/bugs/621918-2.svg
index d9cbd4ff6cb..1f3090babf6 100644
--- a/layout/reftests/bugs/621918-2.svg
+++ b/layout/reftests/bugs/621918-2.svg
@@ -3,6 +3,10 @@
    xmlns:xlink="http://www.w3.org/1999/xlink"
    height="800px"
    width="800px">
+
+ <!-- use an empty g to force filters.svg to load before onload -->
+ <use xlink:href="../filters.svg#empty" />
+
  <g filter="url(../filters.svg#NonWhiteToBlack)">
   <rect x="0" y="0" height="100%" width="100%" fill="#FFFFFF"/>
   <text style="font-size:12px;" transform="translate(40,100)">
diff --git a/layout/reftests/bugs/reftest.list b/layout/reftests/bugs/reftest.list
index d0a986d1839..bc3037440df 100644
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -1571,6 +1571,6 @@ HTTP(..) != 615121-2.html 615121-2-notref.html
 == 621253-1.xhtml 621253-1-ref.xhtml
 HTTP(..) == 619511-1.html 619511-1-ref.html
 random-if(winWidget) == 621918-1.svg 621918-1-ref.svg # 1-pixel diacritic positioning discrepancy in rotated text (may depend on platform fonts)
-HTTP(..) == 621918-2.svg 621918-2-ref.svg # http(..) for filters.svg, used to mask antialiasing issues where glyphs touch
+random-if(winWidget) HTTP(..) == 621918-2.svg 621918-2-ref.svg # same 1px issue as above, and HTTP(..) for filters.svg, used to mask antialiasing issues where glyphs touch
 == 625409-1.html 625409-1-ref.html
 == 627393-1.html about:blank