diff --git a/common/2d/bitmap.cpp b/common/2d/bitmap.cpp
index 81086a83a..f12bd228a 100644
--- a/common/2d/bitmap.cpp
+++ b/common/2d/bitmap.cpp
@@ -90,13 +90,10 @@ void gr_init_bitmap_data (grs_bitmap *bm) // TODO: virtulize
 #endif
 }
 
-grs_bitmap *gr_create_sub_bitmap(grs_bitmap *bm, int x, int y, int w, int h )
+grs_subbitmap_ptr gr_create_sub_bitmap(grs_bitmap *bm, int x, int y, int w, int h )
 {
-	grs_bitmap *n;
-
-	MALLOC(n, grs_bitmap, 1);
-	gr_init_sub_bitmap (n, bm, x, y, w, h);
-
+	grs_subbitmap_ptr n(new grs_bitmap);
+	gr_init_sub_bitmap(n.get(), bm, x, y, w, h);
 	return n;
 }
 
@@ -105,15 +102,6 @@ void gr_free_bitmap(std::unique_ptr<grs_bitmap> bm)
 	gr_free_bitmap_data(bm.get());
 }
 
-void gr_free_sub_bitmap(grs_bitmap *bm )
-{
-	if (bm!=NULL)
-	{
-		d_free(bm);
-	}
-}
-
-
 void gr_free_bitmap_data (grs_bitmap *bm) // TODO: virtulize
 {
 #ifdef OGL
diff --git a/common/include/gr.h b/common/include/gr.h
index 5befe494f..d1452fbd3 100644
--- a/common/include/gr.h
+++ b/common/include/gr.h
@@ -248,16 +248,21 @@ grs_bitmap_ptr gr_create_bitmap(int w,int h);
 // Allocated a bitmap and makes its data be raw_data that is already somewhere.
 grs_bitmap_ptr gr_create_bitmap_raw(int w, int h, unsigned char * raw_data );
 
+// Free the bitmap, but not the pixel data buffer
+struct subbitmap_delete : private std::default_delete<grs_bitmap>
+{
+	using default_delete<grs_bitmap>::operator();
+};
+
+typedef std::unique_ptr<grs_bitmap, subbitmap_delete> grs_subbitmap_ptr;
+
 // Creates a bitmap which is part of another bitmap
-grs_bitmap *gr_create_sub_bitmap(grs_bitmap *bm,int x,int y,int w, int h);
+grs_subbitmap_ptr gr_create_sub_bitmap(grs_bitmap *bm,int x,int y,int w, int h);
 
 // Free the bitmap's data
 void gr_free_bitmap_data (grs_bitmap *bm);
 void gr_init_bitmap_data (grs_bitmap *bm);
 
-// Free the bitmap, but not the pixel data buffer
-void gr_free_sub_bitmap(grs_bitmap *bm);
-
 void gr_bm_pixel( grs_bitmap * bm, int x, int y, unsigned char color );
 void gr_bm_bitblt(int w, int h, int dx, int dy, int sx, int sy, grs_bitmap * src, grs_bitmap * dest);
 void gr_bm_ubitblt( int w, int h, int dx, int dy, int sx, int sy, grs_bitmap * src, grs_bitmap * dest);
diff --git a/similar/main/gauges.cpp b/similar/main/gauges.cpp
index 7663ce173..c471d2f75 100644
--- a/similar/main/gauges.cpp
+++ b/similar/main/gauges.cpp
@@ -347,7 +347,7 @@ bitmap_index Gauges_hires[MAX_GAUGE_BMS];   // hires gauges
 int weapon_box_user[2]={WBU_WEAPON,WBU_WEAPON};		//see WBU_ constants in gauges.h
 #endif
 grs_bitmap deccpt;
-grs_bitmap *WinBoxOverlay[2] = { NULL, NULL }; // Overlay subbitmaps for both weapon boxes
+static array<grs_subbitmap_ptr, 2> WinBoxOverlay; // Overlay subbitmaps for both weapon boxes
 
 #define PAGE_IN_GAUGE(x) _page_in_gauge(x)
 static inline void _page_in_gauge(int x)
@@ -1790,10 +1790,6 @@ static void cockpit_decode_alpha(grs_bitmap *bm)
 #ifdef OGL
 	ogl_ubitmapm_cs (0, 0, -1, -1, &deccpt, 255, F1_0); // render one time to init the texture
 #endif
-	if (WinBoxOverlay[0] != NULL)
-		gr_free_sub_bitmap(WinBoxOverlay[0]);
-	if (WinBoxOverlay[1] != NULL)
-		gr_free_sub_bitmap(WinBoxOverlay[1]);
 	WinBoxOverlay[0] = gr_create_sub_bitmap(&deccpt,(PRIMARY_W_BOX_LEFT)-2,(PRIMARY_W_BOX_TOP)-2,(PRIMARY_W_BOX_RIGHT-PRIMARY_W_BOX_LEFT+4),(PRIMARY_W_BOX_BOT-PRIMARY_W_BOX_TOP+4));
 	WinBoxOverlay[1] = gr_create_sub_bitmap(&deccpt,(SECONDARY_W_BOX_LEFT)-2,(SECONDARY_W_BOX_TOP)-2,(SECONDARY_W_BOX_RIGHT-SECONDARY_W_BOX_LEFT)+4,(SECONDARY_W_BOX_BOT-SECONDARY_W_BOX_TOP)+4);
 
@@ -1814,20 +1810,15 @@ static void draw_wbu_overlay()
 
 	cockpit_decode_alpha(bm);
 
-	if (WinBoxOverlay[0] != NULL)
-		hud_bitblt(HUD_SCALE_X(PRIMARY_W_BOX_LEFT-2),HUD_SCALE_Y(PRIMARY_W_BOX_TOP-2),WinBoxOverlay[0]);
-	if (WinBoxOverlay[1] != NULL)
-		hud_bitblt(HUD_SCALE_X(SECONDARY_W_BOX_LEFT-2),HUD_SCALE_Y(SECONDARY_W_BOX_TOP-2),WinBoxOverlay[1]);
+	if (WinBoxOverlay[0])
+		hud_bitblt(HUD_SCALE_X(PRIMARY_W_BOX_LEFT-2),HUD_SCALE_Y(PRIMARY_W_BOX_TOP-2),WinBoxOverlay[0].get());
+	if (WinBoxOverlay[1])
+		hud_bitblt(HUD_SCALE_X(SECONDARY_W_BOX_LEFT-2),HUD_SCALE_Y(SECONDARY_W_BOX_TOP-2),WinBoxOverlay[1].get());
 }
 
 void close_gauges()
 {
-	if (WinBoxOverlay[0] != NULL)
-		gr_free_sub_bitmap(WinBoxOverlay[0]);
-	if (WinBoxOverlay[1] != NULL)
-		gr_free_sub_bitmap(WinBoxOverlay[1]);
-	WinBoxOverlay[0] = NULL;
-	WinBoxOverlay[1] = NULL;
+	WinBoxOverlay = {};
 }
 
 void init_gauges()
diff --git a/similar/main/newmenu.cpp b/similar/main/newmenu.cpp
index ec30ddb09..209927f25 100644
--- a/similar/main/newmenu.cpp
+++ b/similar/main/newmenu.cpp
@@ -103,16 +103,12 @@ struct newmenu
 };
 
 grs_bitmap nm_background, nm_background1;
-grs_bitmap *nm_background_sub = NULL;
+static grs_subbitmap_ptr nm_background_sub;
 
 void newmenu_free_background()	{
 	if (nm_background.bm_data)
 	{
-		if (nm_background_sub)
-		{
-			gr_free_sub_bitmap(nm_background_sub);
-			nm_background_sub = NULL;
-		}
+		nm_background_sub.reset();
 		gr_free_bitmap_data (&nm_background);
 	}
 	if (nm_background1.bm_data)
@@ -186,12 +182,10 @@ void nm_draw_background(int x1, int y1, int x2, int y2 )
 	if (!init_sub && ((nm_background_sub->bm_w != w*(((float) nm_background.bm_w)/SWIDTH)) || (nm_background_sub->bm_h != h*(((float) nm_background.bm_h)/SHEIGHT))))
 	{
 		init_sub=1;
-		gr_free_sub_bitmap(nm_background_sub);
-		nm_background_sub = NULL;
 	}
 	if (init_sub)
 		nm_background_sub = gr_create_sub_bitmap(&nm_background,0,0,w*(((float) nm_background.bm_w)/SWIDTH),h*(((float) nm_background.bm_h)/SHEIGHT));
-	show_fullscr( nm_background_sub );
+	show_fullscr( nm_background_sub.get() );
 
 	gr_set_current_canvas(old);
 	gr_free_sub_canvas(tmp);