diff --git a/content/svg/content/src/SVGPathData.h b/content/svg/content/src/SVGPathData.h
index 09b2fd712e4..292e8d43073 100644
--- a/content/svg/content/src/SVGPathData.h
+++ b/content/svg/content/src/SVGPathData.h
@@ -23,7 +23,6 @@
 class gfxContext;
 class nsSVGPathDataParser; // IWYU pragma: keep
 
-struct gfxMatrix;
 struct nsSVGMark;
 
 namespace mozilla {
diff --git a/content/svg/content/src/SVGTransform.h b/content/svg/content/src/SVGTransform.h
index 0ee2499f38f..e3d57e8376c 100644
--- a/content/svg/content/src/SVGTransform.h
+++ b/content/svg/content/src/SVGTransform.h
@@ -18,7 +18,7 @@
 
 class nsSVGElement;
 
-struct gfxMatrix;
+class gfxMatrix;
 
 #define MOZ_SVG_LIST_INDEX_BIT_COUNT 31 // supports > 2 billion list items
 
diff --git a/content/svg/content/src/nsSVGElement.h b/content/svg/content/src/nsSVGElement.h
index d54129529fd..e1562a3cd3f 100644
--- a/content/svg/content/src/nsSVGElement.h
+++ b/content/svg/content/src/nsSVGElement.h
@@ -64,7 +64,7 @@ class Matrix;
 
 }
 
-struct gfxMatrix;
+class gfxMatrix;
 struct nsSVGEnumMapping;
 
 typedef nsStyledElementNotElementCSSInlineStyle nsSVGElementBase;
diff --git a/content/svg/content/src/nsSVGPathGeometryElement.h b/content/svg/content/src/nsSVGPathGeometryElement.h
index 770f6db556b..1609713879b 100644
--- a/content/svg/content/src/nsSVGPathGeometryElement.h
+++ b/content/svg/content/src/nsSVGPathGeometryElement.h
@@ -9,7 +9,7 @@
 #include "mozilla/gfx/2D.h"
 #include "SVGGraphicsElement.h"
 
-struct gfxMatrix;
+class gfxMatrix;
 
 struct nsSVGMark {
   enum Type {
diff --git a/gfx/thebes/gfx3DMatrix.h b/gfx/thebes/gfx3DMatrix.h
index 8b7ccd7f9bd..7f884314499 100644
--- a/gfx/thebes/gfx3DMatrix.h
+++ b/gfx/thebes/gfx3DMatrix.h
@@ -11,7 +11,7 @@
 #include <gfxPointH3D.h>
 #include <gfxQuad.h>
 
-struct gfxMatrix;
+class gfxMatrix;
 
 /**
  * This class represents a 3D transformation. The matrix is laid
diff --git a/gfx/thebes/gfxBlur.h b/gfx/thebes/gfxBlur.h
index 67cf757ebae..eafedc3f64c 100644
--- a/gfx/thebes/gfxBlur.h
+++ b/gfx/thebes/gfxBlur.h
@@ -16,7 +16,7 @@ class gfxContext;
 struct gfxRect;
 struct gfxRGBA;
 struct gfxCornerSizes;
-struct gfxMatrix;
+class gfxMatrix;
 
 namespace mozilla {
   namespace gfx {
diff --git a/gfx/thebes/gfxMatrix.h b/gfx/thebes/gfxMatrix.h
index d6297d3423a..5e884fe9254 100644
--- a/gfx/thebes/gfxMatrix.h
+++ b/gfx/thebes/gfxMatrix.h
@@ -30,12 +30,12 @@
  *           \ tx ty 1 /   \         1          /
  *
  */
-struct gfxMatrix {
+class gfxMatrix {
+public:
     double _11; double _12;
     double _21; double _22;
     double _31; double _32;
 
-public:
     /**
      * Initializes this matrix as the identity matrix.
      */
diff --git a/layout/generic/nsIFrame.h b/layout/generic/nsIFrame.h
index 3f74bd2bc7f..7b5bed44d35 100644
--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -60,8 +60,7 @@
 
 struct nsHTMLReflowState;
 class nsHTMLReflowCommand;
-
-struct gfxMatrix;
+class gfxMatrix;
 class nsIAtom;
 class nsPresContext;
 class nsIPresShell;