diff --git a/gfx/thebes/gfxFont.h b/gfx/thebes/gfxFont.h
index d28f1f331e7..252678d0638 100644
--- a/gfx/thebes/gfxFont.h
+++ b/gfx/thebes/gfxFont.h
@@ -1406,6 +1406,16 @@ public:
         return mFontEntry->HasGraphiteTables();
     }
 
+    // Whether this is a font that may be doing full-color rendering,
+    // and therefore needs us to use a mask for text-shadow even when
+    // we're not actually blurring.
+    bool AlwaysNeedsMaskForShadow() {
+        return mFontEntry->TryGetColorGlyphs() ||
+               mFontEntry->TryGetSVGData(this) ||
+               mFontEntry->HasFontTable(TRUETYPE_TAG('C','B','D','T')) ||
+               mFontEntry->HasFontTable(TRUETYPE_TAG('s','b','i','x'));
+    }
+
     // whether a feature is supported by the font (limited to a small set
     // of features for which some form of fallback needs to be implemented)
     bool SupportsFeature(int32_t aScript, uint32_t aFeatureTag);
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index 6321c23cf80..497741f16f5 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -5543,7 +5543,8 @@ nsTextFrame::PaintOneShadow(uint32_t aOffset, uint32_t aLength,
                             const gfxPoint& aFramePt, const gfxPoint& aTextBaselinePt,
                             gfxContext* aCtx, const nscolor& aForegroundColor,
                             const nsCharClipDisplayItem::ClipEdges& aClipEdges,
-                            nscoord aLeftSideOffset, gfxRect& aBoundingBox)
+                            nscoord aLeftSideOffset, gfxRect& aBoundingBox,
+                            uint32_t aBlurFlags)
 {
   PROFILER_LABEL("nsTextFrame", "PaintOneShadow",
     js::ProfileEntry::Category::GRAPHICS);
@@ -5564,7 +5565,8 @@ nsTextFrame::PaintOneShadow(uint32_t aOffset, uint32_t aLength,
   nsContextBoxBlur contextBoxBlur;
   gfxContext* shadowContext = contextBoxBlur.Init(shadowRect, 0, blurRadius,
                                                   PresContext()->AppUnitsPerDevPixel(),
-                                                  aCtx, aDirtyRect, nullptr);
+                                                  aCtx, aDirtyRect, nullptr,
+                                                  aBlurFlags);
   if (!shadowContext)
     return;
 
@@ -6076,13 +6078,28 @@ nsTextFrame::PaintShadows(nsCSSShadowArray* aShadow,
       shadowMetrics.mAdvanceWidth, shadowMetrics.mAscent + shadowMetrics.mDescent);
   shadowMetrics.mBoundingBox.UnionRect(shadowMetrics.mBoundingBox,
                                        decorationRect);
+
+  // If the textrun uses any color or SVG fonts, we need to force use of a mask
+  // for shadow rendering even if blur radius is zero.
+  uint32_t blurFlags = 0;
+  uint32_t numGlyphRuns;
+  const gfxTextRun::GlyphRun* run = mTextRun->GetGlyphRuns(&numGlyphRuns);
+  while (numGlyphRuns-- > 0) {
+    if (run->mFont->AlwaysNeedsMaskForShadow()) {
+      blurFlags = nsContextBoxBlur::FORCE_MASK;
+      break;
+    }
+    run++;
+  }
+
   for (uint32_t i = aShadow->Length(); i > 0; --i) {
     PaintOneShadow(aOffset, aLength,
                    aShadow->ShadowAt(i - 1), &aProvider,
                    aDirtyRect, aFramePt, aTextBaselinePt, aCtx,
                    aForegroundColor, aClipEdges,
                    aLeftEdgeOffset,
-                   shadowMetrics.mBoundingBox);
+                   shadowMetrics.mBoundingBox,
+                   blurFlags);
   }
 }
 
diff --git a/layout/generic/nsTextFrame.h b/layout/generic/nsTextFrame.h
index fa6ef6ea87c..7a085b7caf4 100644
--- a/layout/generic/nsTextFrame.h
+++ b/layout/generic/nsTextFrame.h
@@ -582,7 +582,8 @@ protected:
                       const nscolor& aForegroundColor,
                       const nsCharClipDisplayItem::ClipEdges& aClipEdges,
                       nscoord aLeftSideOffset,
-                      gfxRect& aBoundingBox);
+                      gfxRect& aBoundingBox,
+                      uint32_t aBlurFlags);
 
   void PaintShadows(nsCSSShadowArray* aShadow,
                     uint32_t aOffset, uint32_t aLength,