diff --git a/libImaging/Convert.c b/libImaging/Convert.c
index f4253bda4..e811d9c18 100644
--- a/libImaging/Convert.c
+++ b/libImaging/Convert.c
@@ -536,12 +536,15 @@ rgb2cmyk(UINT8* out, const UINT8* in, int xsize)
 static void
 cmyk2rgb(UINT8* out, const UINT8* in, int xsize)
 {
-    int x;
-    for (x = 0; x < xsize; x++, in += 4) {
-        *out++ = CLIP(255 - (in[0] + in[3]));
-        *out++ = CLIP(255 - (in[1] + in[3]));
-        *out++ = CLIP(255 - (in[2] + in[3]));
-        *out++ = 255;
+    int x, nk, tmp;
+    for (x = 0; x < xsize; x++) {
+        nk = 255 - in[3];
+        out[0] = CLIP(nk - MULDIV255(in[0], nk, tmp));
+        out[1] = CLIP(nk - MULDIV255(in[1], nk, tmp));
+        out[2] = CLIP(nk - MULDIV255(in[2], nk, tmp));
+        out[3] = 255;
+        out += 4;
+        in += 4;
     }
 }