diff --git a/backends/graphics/surfacesdl/surfacesdl-graphics.cpp b/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
index 6434e5c2957..052ae37b9ad 100644
--- a/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
+++ b/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
@@ -1062,7 +1062,7 @@ bool SurfaceSdlGraphicsManager::loadGFXMode() {
 		error("allocating _tmpscreen2 failed");
 
 	// Distinguish 555 and 565 mode
-	if (_hwScreen->format->Rmask == 0x7C00)
+	if (_hwScreen->format->Gmask == 0x3E0)
 		InitScalers(555);
 	else
 		InitScalers(565);
diff --git a/backends/graphics/wincesdl/wincesdl-graphics.cpp b/backends/graphics/wincesdl/wincesdl-graphics.cpp
index 9bfcd640797..caaba1a7dc4 100644
--- a/backends/graphics/wincesdl/wincesdl-graphics.cpp
+++ b/backends/graphics/wincesdl/wincesdl-graphics.cpp
@@ -884,7 +884,7 @@ bool WINCESdlGraphicsManager::loadGFXMode() {
 
 	// Create the surface used for the graphics in 16 bit before scaling, and also the overlay
 	// Distinguish 555 and 565 mode
-	if (_hwScreen->format->Rmask == 0x7C00)
+	if (_hwScreen->format->Gmask == 0x3E0)
 		InitScalers(555);
 	else
 		InitScalers(565);