diff --git a/src/libImaging/PcxDecode.c b/src/libImaging/PcxDecode.c
index 9e9504ce5..e5a38f4be 100644
--- a/src/libImaging/PcxDecode.c
+++ b/src/libImaging/PcxDecode.c
@@ -22,10 +22,7 @@ ImagingPcxDecode(Imaging im, ImagingCodecState state, UINT8* buf, Py_ssize_t byt
     UINT8 n;
     UINT8* ptr;
 
-    if (strcmp(im->mode, "1") == 0 && state->xsize > state->bytes * 8) {
-        state->errcode = IMAGING_CODEC_OVERRUN;
-        return -1;
-    } else if (strcmp(im->mode, "P") == 0 && state->xsize > state->bytes) {
+    if ((state->xsize * state->bits + 7) / 8 > state->bytes) {
         state->errcode = IMAGING_CODEC_OVERRUN;
         return -1;
     }