diff --git a/jcmaster.c b/jcmaster.c
index 733ed3b6..f448ec41 100644
--- a/jcmaster.c
+++ b/jcmaster.c
@@ -332,11 +332,11 @@ select_scan_parameters (j_compress_ptr cinfo)
   if (master->pass_number < master->pass_number_scan_opt_base) {
     cinfo->comps_in_scan = 1;
     if (cinfo->use_scans_in_trellis) {
-      cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/4];
+      cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/(4*cinfo->trellis_num_loops)];
       cinfo->Ss = (master->pass_number%4 < 2) ? 1 : cinfo->trellis_freq_split+1;
       cinfo->Se = (master->pass_number%4 < 2) ? cinfo->trellis_freq_split : DCTSIZE2-1;
     } else {
-      cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/2];
+      cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/(2*cinfo->trellis_num_loops)];
       cinfo->Ss = 1;
       cinfo->Se = DCTSIZE2-1;
     }
@@ -900,7 +900,7 @@ jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
   
   if (cinfo->trellis_quant) {
     if (cinfo->progressive_mode)
-      master->total_passes += ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components;
+      master->total_passes += ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components * cinfo->trellis_num_loops;
     else
       master->total_passes += 1;
   }
@@ -912,6 +912,6 @@ jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
     for (i = 0; i < cinfo->num_scans; i++)
       master->scan_buffer[i] = NULL;
     
-    master->pass_number_scan_opt_base = ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components;
+    master->pass_number_scan_opt_base = ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components * cinfo->trellis_num_loops;
   }
 }
diff --git a/jcparam.c b/jcparam.c
index 514ecd01..883f9262 100644
--- a/jcparam.c
+++ b/jcparam.c
@@ -432,6 +432,7 @@ jpeg_set_defaults (j_compress_ptr cinfo)
   
   cinfo->use_scans_in_trellis = FALSE;
   cinfo->trellis_freq_split = 8;
+  cinfo->trellis_num_loops = 1;
 }
 
 
diff --git a/jpeglib.h b/jpeglib.h
index 7a4fc132..23c3c846 100644
--- a/jpeglib.h
+++ b/jpeglib.h
@@ -386,6 +386,7 @@ struct jpeg_compress_struct {
   boolean trellis_passes; /* TRUE=currently doing trellis-related passes */
   
   int trellis_freq_split; /* splitting point for frequency in trellis quantization */
+  int trellis_num_loops; /* number of trellis loops */
   
   int num_scans_luma; /* # of entries in scan_info array pertaining to luma (used when optimize_scans is TRUE */
   int num_scans_luma_dc;