diff --git a/coders/xbm.c b/coders/xbm.c
index 57724ad..1cc444a 100644
--- a/coders/xbm.c
+++ b/coders/xbm.c
@@ -547,7 +547,7 @@
     for (x=0; x < (ssize_t) image->columns; x++)
     {
       byte>>=1;
-      if (GetPixelIntensity(image,p) < (QuantumRange/2))
+      if (GetPixelLuma(image,p) < (QuantumRange/2))
         byte|=0x80;
       bit++;
       if (bit == 8)