diff --git a/exec/xbimage.js b/exec/xbimage.js
index b8d47ef872e1ef356cd46203b258bd365aababdc..349d60e6a73dff7413e31ee4baa7ace6fcd46649 100644
--- a/exec/xbimage.js
+++ b/exec/xbimage.js
@@ -1,5 +1,3 @@
-// $Id: xbimage.js,v 1.6 2020/04/19 19:52:31 rswindell Exp $
-
 // Utility module for creating and displaying XBin image files.
 
 load('sbbsdefs.js');
@@ -34,6 +32,11 @@ function convert_from_bmp(filename, charheight, fg_color, bg_color, palette, inv
 		return false;
 	}
 
+	if(bmp.infoheader.biBitCount != 1) {
+		alert(format("Bit-count (%d) must be 1 (monochrome)", bmp.infoheader.biBitCount));
+		return false;
+	}
+
 	// Add SAUCE 
 	var sauce = {
 		 title: title ? title : filename