diff --git a/src/heretic/am_map.c b/src/heretic/am_map.c
index 32a3f7b50b..386b6c2b2c 100644
--- a/src/heretic/am_map.c
+++ b/src/heretic/am_map.c
@@ -1118,6 +1118,7 @@ void AM_clearFB(int color)
 
     for (i = 0; i < finit_height; i++)
     {
+#ifndef CRISPY_TRUECOLOR
         memcpy(I_VideoBuffer + i * finit_width,
                maplump + j + (MAPBGROUNDWIDTH << crispy->hires) - x3, x3);
 
@@ -1126,7 +1127,30 @@ void AM_clearFB(int color)
 
         memcpy(I_VideoBuffer + i * finit_width + x2 + x3,
                maplump + j, x1);
+#else
+        int z;
+        pixel_t *dest = I_VideoBuffer + i * finit_width;
+        byte *src = maplump + j + (MAPBGROUNDWIDTH << crispy->hires) - x3;
+
+        for (z = 0; z < x3; z++)
+        {
+            dest[z] = colormaps[src[z]];
+        }
 
+        dest += x3;
+        src += x3 - x2;
+        for (z = 0; z < x2; z++)
+        {
+            dest[z] = colormaps[src[z]];
+        }
+
+        dest += x2;
+        src = maplump + j;
+        for (z = 0; z < x1; z++)
+        {
+            dest[z] = colormaps[src[z]];
+        }
+#endif
         j += MAPBGROUNDWIDTH << crispy->hires;
         if (j >= MAPBGROUNDHEIGHT * MAPBGROUNDWIDTH)
             j = 0;