diff --git a/gdk/macos/gdkmacosglcontext.c b/gdk/macos/gdkmacosglcontext.c
index d3c70e6f5b..e3d72e54d9 100644
--- a/gdk/macos/gdkmacosglcontext.c
+++ b/gdk/macos/gdkmacosglcontext.c
@@ -21,6 +21,7 @@
 
 #include "gdkmacosglcontext-private.h"
 #include "gdkmacossurface-private.h"
+#include "gdkmacostoplevelsurface-private.h"
 
 #include "gdkinternals.h"
 #include "gdkintl.h"
@@ -174,7 +175,6 @@ gdk_macos_gl_context_real_realize (GdkGLContext  *context,
   GdkGLContext *shared_data;
   GdkGLContext *existing;
   GLint sync_to_framerate = 1;
-  GLint opaque = 0;
   GLint validate = 0;
   int major, minor;
 
@@ -225,7 +225,6 @@ gdk_macos_gl_context_real_realize (GdkGLContext  *context,
     }
 
   [gl_context setValues:&sync_to_framerate forParameter:NSOpenGLCPSwapInterval];
-  [gl_context setValues:&opaque forParameter:NSOpenGLCPSurfaceOpacity];
   [gl_context setValues:&validate forParameter:NSOpenGLContextParameterStateValidation];
 
   self->dummy_window = [[NSWindow alloc] initWithContentRect:NSZeroRect
@@ -280,6 +279,9 @@ gdk_macos_gl_context_begin_frame (GdkDrawContext *context,
 
   if (self->needs_resize)
     {
+      GdkSurface *surface = gdk_draw_context_get_surface (context);
+      GLint opaque;
+
       self->needs_resize = FALSE;
 
       if (self->dummy_view != NULL)
@@ -291,6 +293,16 @@ gdk_macos_gl_context_begin_frame (GdkDrawContext *context,
           [self->dummy_view setFrame:frame];
         }
 
+      /* Possibly update our opaque setting depending on a resize. We can
+       * rely on getting a resize if decoarated is changed, so this reduces
+       * how much we adjust the parameter.
+       */
+      if (GDK_IS_MACOS_TOPLEVEL_SURFACE (surface))
+        opaque = GDK_MACOS_TOPLEVEL_SURFACE (surface)->decorated;
+      else
+        opaque = FALSE;
+      [self->gl_context setValues:&opaque forParameter:NSOpenGLCPSurfaceOpacity];
+
       [self->gl_context update];
     }
 
diff --git a/gdk/macos/gdkmacostoplevelsurface-private.h b/gdk/macos/gdkmacostoplevelsurface-private.h
index d7866601e5..8d3ec15b02 100644
--- a/gdk/macos/gdkmacostoplevelsurface-private.h
+++ b/gdk/macos/gdkmacostoplevelsurface-private.h
@@ -24,13 +24,24 @@
 
 G_BEGIN_DECLS
 
-typedef struct _GdkMacosToplevelSurface      GdkMacosToplevelSurface;
-typedef struct _GdkMacosToplevelSurfaceClass GdkMacosToplevelSurfaceClass;
-
 #define GDK_TYPE_MACOS_TOPLEVEL_SURFACE       (_gdk_macos_toplevel_surface_get_type())
 #define GDK_MACOS_TOPLEVEL_SURFACE(object)    (G_TYPE_CHECK_INSTANCE_CAST ((object), GDK_TYPE_MACOS_TOPLEVEL_SURFACE, GdkMacosToplevelSurface))
 #define GDK_IS_MACOS_TOPLEVEL_SURFACE(object) (G_TYPE_CHECK_INSTANCE_TYPE ((object), GDK_TYPE_MACOS_TOPLEVEL_SURFACE))
 
+typedef struct _GdkMacosToplevelSurface      GdkMacosToplevelSurface;
+typedef struct _GdkMacosToplevelSurfaceClass GdkMacosToplevelSurfaceClass;
+
+struct _GdkMacosToplevelSurface
+{
+  GdkMacosSurface parent_instance;
+  guint           decorated : 1;
+};
+
+struct _GdkMacosToplevelSurfaceClass
+{
+  GdkMacosSurfaceClass parent_instance;
+};
+
 GType            _gdk_macos_toplevel_surface_get_type           (void);
 GdkMacosSurface *_gdk_macos_toplevel_surface_new                (GdkMacosDisplay *display,
                                                                  GdkSurface      *parent,
diff --git a/gdk/macos/gdkmacostoplevelsurface.c b/gdk/macos/gdkmacostoplevelsurface.c
index 2615957b2c..a9a6488419 100644
--- a/gdk/macos/gdkmacostoplevelsurface.c
+++ b/gdk/macos/gdkmacostoplevelsurface.c
@@ -29,17 +29,6 @@
 #include "gdkmacostoplevelsurface-private.h"
 #include "gdkmacosutils-private.h"
 
-struct _GdkMacosToplevelSurface
-{
-  GdkMacosSurface parent_instance;
-  guint           decorated : 1;
-};
-
-struct _GdkMacosToplevelSurfaceClass
-{
-  GdkMacosSurfaceClass parent_instance;
-};
-
 static void
 _gdk_macos_toplevel_surface_fullscreen (GdkMacosToplevelSurface *self)
 {