diff --git a/mozilla/layout/base/nsCSSRendering.cpp b/mozilla/layout/base/nsCSSRendering.cpp
index 88cdf11ccc2..0e2db8aa10e 100644
--- a/mozilla/layout/base/nsCSSRendering.cpp
+++ b/mozilla/layout/base/nsCSSRendering.cpp
@@ -1638,8 +1638,8 @@ void nsCSSRendering::PaintBorderEdges(nsIPresContext& aPresContext,
 // -(aTileWidth - 1) <= anchor.x <= 0
 // -(aTileHeight - 1) <= anchor.y <= 0
 //
-// i.e., they are either 0 or a negative number which is less than the
-// tile size in that dimension
+// i.e., they are either 0 or a negative number whose absolute value is
+// less than the tile size in that dimension
 static void
 ComputeBackgroundAnchorPoint(const nsStyleColor& aColor,
                              const nsRect& aBounds,
diff --git a/mozilla/layout/html/style/src/nsCSSRendering.cpp b/mozilla/layout/html/style/src/nsCSSRendering.cpp
index 88cdf11ccc2..0e2db8aa10e 100644
--- a/mozilla/layout/html/style/src/nsCSSRendering.cpp
+++ b/mozilla/layout/html/style/src/nsCSSRendering.cpp
@@ -1638,8 +1638,8 @@ void nsCSSRendering::PaintBorderEdges(nsIPresContext& aPresContext,
 // -(aTileWidth - 1) <= anchor.x <= 0
 // -(aTileHeight - 1) <= anchor.y <= 0
 //
-// i.e., they are either 0 or a negative number which is less than the
-// tile size in that dimension
+// i.e., they are either 0 or a negative number whose absolute value is
+// less than the tile size in that dimension
 static void
 ComputeBackgroundAnchorPoint(const nsStyleColor& aColor,
                              const nsRect& aBounds,