diff --git a/src/r_draw_pal.cpp b/src/r_draw_pal.cpp
index 15846977de..90dcc9c3b3 100644
--- a/src/r_draw_pal.cpp
+++ b/src/r_draw_pal.cpp
@@ -1610,9 +1610,9 @@ namespace swrenderer
 				int src_g = ((_srccolor >> 0) & 0xff) * _srcalpha;
 				int src_b = ((_srccolor >> 8) & 0xff) * _srcalpha;
 				int bg = *dest;
-				int r = MAX((src_r * _srcalpha - palette[bg].r * _destalpha)>>18, 0);
-				int g = MAX((src_g * _srcalpha - palette[bg].g * _destalpha)>>18, 0);
-				int b = MAX((src_b * _srcalpha - palette[bg].b * _destalpha)>>18, 0);
+				int r = MAX((-src_r + palette[bg].r * _destalpha)>>18, 0);
+				int g = MAX((-src_g + palette[bg].g * _destalpha)>>18, 0);
+				int b = MAX((-src_b + palette[bg].b * _destalpha)>>18, 0);
 
 				*dest = RGB256k.RGB[r][g][b];
 				dest += pitch;
@@ -1667,9 +1667,9 @@ namespace swrenderer
 				int src_g = ((_srccolor >> 0) & 0xff) * _srcalpha;
 				int src_b = ((_srccolor >> 8) & 0xff) * _srcalpha;
 				int bg = *dest;
-				int r = MAX((src_r * _srcalpha - palette[bg].r * _destalpha)>>18, 0);
-				int g = MAX((src_g * _srcalpha - palette[bg].g * _destalpha)>>18, 0);
-				int b = MAX((src_b * _srcalpha - palette[bg].b * _destalpha)>>18, 0);
+				int r = MAX((src_r - palette[bg].r * _destalpha)>>18, 0);
+				int g = MAX((src_g - palette[bg].g * _destalpha)>>18, 0);
+				int b = MAX((src_b - palette[bg].b * _destalpha)>>18, 0);
 
 				*dest = RGB256k.RGB[r][g][b];
 				dest += pitch;