diff --git a/src/hq4x.c b/src/hq4x.c
index 5614ef64d..749ced580 100644
--- a/src/hq4x.c
+++ b/src/hq4x.c
@@ -178,9 +178,9 @@ void hq4x_32(SDL_Surface * src, SDL_Surface * dest,
   int prevline, nextline;
   Uint16 w[10];
   Uint8 a;
-  Uint32 YUV1, YUV2;
   int pattern;
   int flag;
+  Uint32 YUV1, YUV2;
 
   
   /*
diff --git a/src/hqxx.c b/src/hqxx.c
index 7bc8b1566..596c2254b 100644
--- a/src/hqxx.c
+++ b/src/hqxx.c
@@ -181,7 +181,9 @@ void InitLUTs(Uint32 * RGBtoYUV)
 	      Y = (r + g + b) >> 2;
 	      u = 128 + ((r - b) >> 2);
 	      v = 128 + ((-r + 2 * g - b) >> 3);
-	      RGBtoYUV[(i << 11) + (j << 5) + k] = (Y << 16) + (u << 8) + v;
+	      RGBtoYUV[(i << 11) + (j << 5) + k] = (((Y & 0xF8) << 8) |
+						    ((u & 0xFE) << 3) |
+						    (v >> 3));
 	    }
 	}
     }
@@ -208,11 +210,15 @@ inline void Interp2(SDL_Surface * dest, int x, int y, Uint16 c1, Uint16 c2, Uint
 {
   Uint32 c;
 
+  /* FIXME? */
+  
   // c = (c1 * 2 + c2 + c3) >> 2;
 
   c = ((((c1 & 0x07E0) * 2 + (c2 & 0x07E0) + (c3 & 0x07E0)) & (0x07E0 << 2)) +
        (((c1 & 0xF81F) * 2 + (c2 & 0xF81F) + (c3 & 0xF81F)) & (0xF81F << 2)))
 								      >> 2;
+
+
   hqxx_putpixel(dest, x, y, c, alpha);
 }
 
@@ -246,7 +252,7 @@ inline void Interp4(SDL_Surface * dest, int x, int y, Uint16 c1, Uint16 c2, Uint
   
   c = ((((c1 & 0x07E0) * 2 +
 	 ((c2 & 0x07E0) +
-	  (c3 & 0x07E0)) * 7) & 0x07E00) +
+	  (c3 & 0x07E0)) * 7) & 0x7E00) +
        (((c1 & 0xF81F) * 2 +
 	 ((c2 & 0xF81F) +
 	  (c3 & 0xF81F)) * 7) & 0xF81F0)) >> 4;
diff --git a/src/hqxx.h b/src/hqxx.h
index 856f98bc6..8a38a9ede 100644
--- a/src/hqxx.h
+++ b/src/hqxx.h
@@ -27,21 +27,17 @@
 
 #include "SDL.h"
 
-#define Ymask 0x00FF0000
-#define Umask 0x0000FF00
-#define Vmask 0x000000FF
+#define Ymask 0xF800
+#define Umask 0x07E0
+#define Vmask 0x001F
 
-//#define Ymask 0xF800
-//#define Umask 0x07E0
-//#define Vmask 0x001F
+//trY in 32 = 0x00300000
+//trU in 32 = 0x00000700
+//trV in 32 = 0x00000006
 
-#define trY 0x00300000
-#define trU 0x00000700
-#define trV 0x00000006
-
-//#define trY   0x3000
-//#define trU   0x00C0
-//#define trV   0x0006
+#define trY   0x3000
+#define trU   0x00C0
+#define trV   0x0006
 
 
 Uint16 hqxx_getpixel(SDL_Surface * surface, int x, int y, Uint8 * alpha);
diff --git a/src/tuxpaint.c b/src/tuxpaint.c
index 34b75e245..04b4b0aa7 100644
--- a/src/tuxpaint.c
+++ b/src/tuxpaint.c
@@ -38,7 +38,7 @@
 /* #define USE_HWSURFACE */
 
 
-/* #define USE_HQ4X */
+#define USE_HQ4X
 
 
 /* Disable fancy cursors in fullscreen mode, to avoid SDL bug: */
@@ -3007,7 +3007,7 @@ void stamp_draw(int x, int y)
   
   /* Shrink or grow it! */
 
-#ifdef HQ4X
+#ifdef USE_HQ4X
   if (state_stamps[cur_stamp]->size == 400)
     {
       /* Use high quality 4x filter! */