diff --git a/src/libImaging/Reduce.c b/src/libImaging/Reduce.c
index 32d66eefb..b4bfc728e 100644
--- a/src/libImaging/Reduce.c
+++ b/src/libImaging/Reduce.c
@@ -1157,8 +1157,8 @@ ImagingReduceCorners(Imaging imOut, Imaging imIn, int box[4], int xscale, int ys
                         ss1 += line[xx * 2 + 1];
                     }
                 }
-                ((UINT8 *)imOut->image[y])[x + 0] = (ss0 * multiplier) >> 24;
-                ((UINT8 *)imOut->image[y])[x + 1] = (ss1 * multiplier) >> 24;
+                ((UINT8 *)imOut->image[y])[x * 2 + 0] = (ss0 * multiplier) >> 24;
+                ((UINT8 *)imOut->image[y])[x * 2 + 1] = (ss1 * multiplier) >> 24;
             }
         }
         if (box[3] % yscale) {
@@ -1176,8 +1176,8 @@ ImagingReduceCorners(Imaging imOut, Imaging imIn, int box[4], int xscale, int ys
                         ss1 += line[xx * 2 + 1];
                     }
                 }
-                ((UINT8 *)imOut->image[y])[x + 0] = (ss0 * multiplier) >> 24;
-                ((UINT8 *)imOut->image[y])[x + 1] = (ss1 * multiplier) >> 24;
+                ((UINT8 *)imOut->image[y])[x * 2 + 0] = (ss0 * multiplier) >> 24;
+                ((UINT8 *)imOut->image[y])[x * 2 + 1] = (ss1 * multiplier) >> 24;
             }
         }
         if (box[2] % xscale && box[3] % yscale) {
@@ -1194,8 +1194,8 @@ ImagingReduceCorners(Imaging imOut, Imaging imIn, int box[4], int xscale, int ys
                     ss1 += line[xx * 2 + 1];
                 }
             }
-            ((UINT8 *)imOut->image[y])[x + 0] = (ss0 * multiplier) >> 24;
-            ((UINT8 *)imOut->image[y])[x + 1] = (ss1 * multiplier) >> 24;
+            ((UINT8 *)imOut->image[y])[x * 2 + 0] = (ss0 * multiplier) >> 24;
+            ((UINT8 *)imOut->image[y])[x * 2 + 1] = (ss1 * multiplier) >> 24;
         }
     } else if (imIn->pixelsize == 4) {
         if (box[2] % xscale) {