diff --git a/common/rfb/JpegCompressor.cxx b/common/rfb/JpegCompressor.cxx
index 7a870b0..33f6c41 100644
--- a/common/rfb/JpegCompressor.cxx
+++ b/common/rfb/JpegCompressor.cxx
@@ -194,6 +194,8 @@
     cinfo.comp_info[0].h_samp_factor = 2;
     cinfo.comp_info[0].v_samp_factor = 1;
     break;
+  case SUBSAMP_GRAY:
+    jpeg_set_colorspace(&cinfo, JCS_GRAYSCALE);
   default:
     cinfo.comp_info[0].h_samp_factor = 1;
     cinfo.comp_info[0].v_samp_factor = 1;