--- a/gfx/2d/ScaledFontDWrite.cpp
+++ b/gfx/2d/ScaledFontDWrite.cpp
@@ -309,16 +309,17 @@ ScaledFontDWrite::GetWRFontInstanceOptio
 {
   AntialiasMode aaMode = GetDefaultAAMode();
   if (aaMode != AntialiasMode::SUBPIXEL) {
     wr::FontInstanceOptions options;
     options.render_mode =
       aaMode == AntialiasMode::NONE ? wr::FontRenderMode::Mono : wr::FontRenderMode::Alpha;
     options.subpx_dir = wr::SubpixelDirection::Horizontal;
     options.synthetic_italics = false;
+    options.bg_color = wr::ToColorU(Color());
     *aOutOptions = Some(options);
   }
 
   wr::FontInstancePlatformOptions platformOptions;
   platformOptions.use_embedded_bitmap = UseEmbeddedBitmaps();
   platformOptions.force_gdi_rendering = ForceGDIMode();
   *aOutPlatformOptions = Some(platformOptions);
   return true;

--- a/gfx/2d/ScaledFontFontconfig.cpp
+++ b/gfx/2d/ScaledFontFontconfig.cpp
@@ -248,16 +248,17 @@ bool
 ScaledFontFontconfig::GetWRFontInstanceOptions(Maybe<wr::FontInstanceOptions>* aOutOptions,
                                                Maybe<wr::FontInstancePlatformOptions>* aOutPlatformOptions,
                                                std::vector<FontVariation>* aOutVariations)
 {
   wr::FontInstanceOptions options;
   options.render_mode = wr::FontRenderMode::Alpha;
   options.subpx_dir = wr::SubpixelDirection::Horizontal;
   options.synthetic_italics = false;
+  options.bg_color = wr::ToColorU(Color());
 
   wr::FontInstancePlatformOptions platformOptions;
   platformOptions.flags = 0;
   platformOptions.lcd_filter = wr::FontLCDFilter::Legacy;
   platformOptions.hinting = wr::FontHinting::Normal;
 
   FcBool autohint;
   if (FcPatternGetBool(mPattern, FC_AUTOHINT, 0, &autohint) == FcResultMatch && autohint) {

--- a/gfx/webrender_bindings/WebRenderTypes.h
+++ b/gfx/webrender_bindings/WebRenderTypes.h
@@ -254,16 +254,26 @@ static inline wr::ColorF ToColorF(const 
   wr::ColorF c;
   c.r = color.r;
   c.g = color.g;
   c.b = color.b;
   c.a = color.a;
   return c;
 }
 
+static inline wr::ColorU ToColorU(const gfx::Color& color)
+{
+  wr::ColorU c;
+  c.r = uint8_t(color.r * 255.0f);
+  c.g = uint8_t(color.g * 255.0f);
+  c.b = uint8_t(color.b * 255.0f);
+  c.a = uint8_t(color.a * 255.0f);
+  return c;
+}
+
 static inline wr::LayoutPoint ToLayoutPoint(const mozilla::LayoutDevicePoint& point)
 {
   wr::LayoutPoint p;
   p.x = point.x;
   p.y = point.y;
   return p;
 }