diff --git a/src/Tk/tkImaging.c b/src/Tk/tkImaging.c
index a36c3e0bd..3e35f885f 100644
--- a/src/Tk/tkImaging.c
+++ b/src/Tk/tkImaging.c
@@ -121,15 +121,18 @@ PyImagingPhotoPut(
 
     /* Mode */
 
-    if (strcmp(im->mode, "1") == 0 || strcmp(im->mode, "L") == 0) {
+    if (im->mode == IMAGING_MODE_1 || im->mode == IMAGING_MODE_L) {
         block.pixelSize = 1;
         block.offset[0] = block.offset[1] = block.offset[2] = block.offset[3] = 0;
-    } else if (strncmp(im->mode, "RGB", 3) == 0) {
+    } else if (
+        im->mode == IMAGING_MODE_RGB || im->mode == IMAGING_MODE_RGBA ||
+        im->mode == IMAGING_MODE_RGBX || im->mode == IMAGING_MODE_RGBa
+    ) {
         block.pixelSize = 4;
         block.offset[0] = 0;
         block.offset[1] = 1;
         block.offset[2] = 2;
-        if (strcmp(im->mode, "RGBA") == 0) {
+        if (im->mode == IMAGING_MODE_RGBA) {
             block.offset[3] = 3; /* alpha (or reserved, under Tk 8.2) */
         } else {
             block.offset[3] = 0; /* no alpha */