diff --git a/backend/genesys.cc b/backend/genesys.cc
index 8bd147401..4f8a1a06a 100644
--- a/backend/genesys.cc
+++ b/backend/genesys.cc
@@ -3432,8 +3432,7 @@ static void genesys_fill_line_interp_buffer(Genesys_Device* dev, uint8_t* work_b
           dev->cur++;
 
 	  /* go to next line if needed */
-	  if (dev->cur == dev->len)
-	    {
+        if (dev->cur == dev->deseg.pixel_groups) {
               dev->oe_buffer.set_pos(dev->oe_buffer.pos() + dev->deseg.raw_channel_bytes);
 	      dev->cur = 0;
               dev->line_count++;
@@ -3476,7 +3475,7 @@ static void genesys_fill_segmented_buffer(Genesys_Device* dev, uint8_t* work_buf
       while (count < size)
 	{
             if (depth==1) {
-                while (dev->cur < dev->len && count < size) {
+                while (dev->cur < dev->deseg.pixel_groups && count < size) {
                     for (n=0; n<dev->segnb; n++) {
                         work_buffer_dst[count+n] = 0;
                     }
@@ -3497,7 +3496,7 @@ static void genesys_fill_segmented_buffer(Genesys_Device* dev, uint8_t* work_buf
                 }
             }
             if (depth==8) {
-                 while (dev->cur < dev->len && count < size) {
+                 while (dev->cur < dev->deseg.pixel_groups && count < size) {
                     for (n=0;n<dev->segnb;n++) {
                         work_buffer_dst[count+n] = dev->oe_buffer.get_read_pos()[dev->cur + dev->skip + dev->deseg.conseq_pixel_dist_bytes *dev->segment_order[n]];
                     }
@@ -3507,7 +3506,7 @@ static void genesys_fill_segmented_buffer(Genesys_Device* dev, uint8_t* work_buf
                 }
             }
             if (depth==16) {
-                while (dev->cur < dev->len && count < size) {
+                while (dev->cur < dev->deseg.pixel_groups && count < size) {
                     for (n=0;n<dev->segnb;n++) {
                         work_buffer_dst[count+n*2] = dev->oe_buffer.get_read_pos()[dev->cur + dev->skip + dev->deseg.conseq_pixel_dist_bytes * dev->segment_order[n]];
                         work_buffer_dst[count+n*2+1] = dev->oe_buffer.get_read_pos()[dev->cur + dev->skip + dev->deseg.conseq_pixel_dist_bytes * dev->segment_order[n] + 1];
@@ -3519,8 +3518,7 @@ static void genesys_fill_segmented_buffer(Genesys_Device* dev, uint8_t* work_buf
             }
 
 	  /* go to next line if needed */
-	  if (dev->cur == dev->len)
-	    {
+        if (dev->cur == dev->deseg.pixel_groups) {
               dev->oe_buffer.set_pos(dev->oe_buffer.pos() + dev->deseg.raw_channel_bytes);
 	      dev->cur = 0;
 	    }
diff --git a/backend/genesys_device.h b/backend/genesys_device.h
index 378b857e4..7eb0eb890 100644
--- a/backend/genesys_device.h
+++ b/backend/genesys_device.h
@@ -195,11 +195,17 @@ struct Genesys_Model
 // Describes the geometry of the raw data coming out of the scanner for desegmentation.
 struct DesegmentationState
 {
+    // The number of "even" pixels to scan. This corresponds to the number of pixels that will be
+    // scanned from a single segment
+    unsigned pixel_groups = 0;
+
     // Distance in bytes between consecutive pixels, e.g. between odd and even pixels. Note that
     // the number of segments can be large.
     unsigned conseq_pixel_dist_bytes = 0;
+
     // Total bytes in a channel received from a scanner
     unsigned raw_channel_bytes = 0;
+
     // Total bytes in a line received from a scanner
     unsigned raw_line_bytes = 0;
 };
@@ -328,8 +334,6 @@ struct Genesys_Device
     int line_interp = 0;
     // number of scan lines used during scan
     int line_count = 0;
-    // number of even pixels
-    size_t len = 0;
     // current pixel position within sub window
     size_t cur = 0;
     // number of bytes to skip at start of line
diff --git a/backend/genesys_gl124.cc b/backend/genesys_gl124.cc
index 1f8cfaebe..9ccf258d3 100644
--- a/backend/genesys_gl124.cc
+++ b/backend/genesys_gl124.cc
@@ -997,7 +997,7 @@ static void gl124_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
 
   dev->cur = 0;
   dev->skip = 0;
-    dev->len = dev->deseg.raw_channel_bytes / segnb;
+    dev->deseg.pixel_groups = dev->deseg.raw_channel_bytes / segnb;
     dev->deseg.conseq_pixel_dist_bytes = dev->deseg.raw_channel_bytes / segnb;
   dev->segnb = segnb;
   dev->line_count = 0;
@@ -1006,7 +1006,7 @@ static void gl124_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG (DBG_io2, "%s: pixels          =%d\n", __func__, session.optical_pixels);
   DBG (DBG_io2, "%s: depth           =%d\n", __func__, session.params.depth);
   DBG (DBG_io2, "%s: dev->bpl        =%lu\n", __func__, (unsigned long) dev->deseg.raw_channel_bytes);
-  DBG (DBG_io2, "%s: dev->len        =%lu\n", __func__, (unsigned long)dev->len);
+  DBG (DBG_io2, "%s: dev->len        =%lu\n", __func__, (unsigned long) dev->deseg.pixel_groups);
   DBG (DBG_io2, "%s: dev->dist       =%lu\n", __func__, (unsigned long) dev->deseg.conseq_pixel_dist_bytes);
   DBG (DBG_io2, "%s: dev->line_interp=%lu\n", __func__, (unsigned long)dev->line_interp);
 
diff --git a/backend/genesys_gl843.cc b/backend/genesys_gl843.cc
index a5ef81688..f519c411a 100644
--- a/backend/genesys_gl843.cc
+++ b/backend/genesys_gl843.cc
@@ -1163,7 +1163,7 @@ static void gl843_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG(DBG_io2, "%s: pixels     =%d\n", __func__, session.optical_pixels);
   DBG(DBG_io2, "%s: depth      =%d\n", __func__, session.params.depth);
   DBG(DBG_io2, "%s: dev->bpl   =%lu\n", __func__, (unsigned long) dev->deseg.raw_channel_bytes);
-  DBG(DBG_io2, "%s: dev->len   =%lu\n", __func__, (unsigned long)dev->len);
+  DBG(DBG_io2, "%s: dev->len   =%lu\n", __func__, (unsigned long) dev->deseg.pixel_groups);
   DBG(DBG_io2, "%s: dev->dist  =%lu\n", __func__, (unsigned long) dev->deseg.conseq_pixel_dist_bytes);
 
   /* MAXWD is expressed in 2 words unit */
diff --git a/backend/genesys_gl846.cc b/backend/genesys_gl846.cc
index 055c67fe9..dffc54474 100644
--- a/backend/genesys_gl846.cc
+++ b/backend/genesys_gl846.cc
@@ -761,7 +761,7 @@ static void gl846_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
     // compute pixel coordinate in the given dpihw space, taking segments into account
     startx /= factor*segnb;
     endx /= factor*segnb;
-    dev->len = endx - startx;
+    dev->deseg.pixel_groups = endx - startx;
     dev->deseg.conseq_pixel_dist_bytes = 0;
   dev->skip=0;
 
@@ -872,7 +872,7 @@ static void gl846_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   /* words(16bit) before gamma, conversion to 8 bit or lineart*/
   words_per_line = (used_pixels * session.params.xres * ccd_pixels_per_system_pixel) / sensor.get_register_hwdpi(session.params.xres * ccd_pixels_per_system_pixel);
     dev->deseg.raw_channel_bytes = multiply_by_depth_ceil(words_per_line, session.params.depth);
-    dev->len = multiply_by_depth_ceil(dev->len, session.params.depth);
+    dev->deseg.pixel_groups = multiply_by_depth_ceil(dev->deseg.pixel_groups, session.params.depth);
     dev->deseg.conseq_pixel_dist_bytes = multiply_by_depth_ceil(dev->deseg.conseq_pixel_dist_bytes, session.params.depth);
 
   dev->cur=0;
@@ -892,7 +892,7 @@ static void gl846_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG (DBG_io2, "%s: pixels     =%d\n", __func__, session.optical_pixels);
   DBG (DBG_io2, "%s: depth      =%d\n", __func__, session.params.depth);
   DBG (DBG_io2, "%s: dev->bpl   =%lu\n", __func__, (unsigned long) dev->deseg.raw_channel_bytes);
-  DBG (DBG_io2, "%s: dev->len   =%lu\n", __func__, (unsigned long)dev->len);
+  DBG (DBG_io2, "%s: dev->len   =%lu\n", __func__, (unsigned long) dev->deseg.pixel_groups);
   DBG (DBG_io2, "%s: dev->dist  =%lu\n", __func__, (unsigned long) dev->deseg.conseq_pixel_dist_bytes);
   DBG (DBG_io2, "%s: dev->segnb =%lu\n", __func__, (unsigned long)dev->segnb);
 
diff --git a/backend/genesys_gl847.cc b/backend/genesys_gl847.cc
index fd73c9726..fa59359f1 100644
--- a/backend/genesys_gl847.cc
+++ b/backend/genesys_gl847.cc
@@ -780,7 +780,7 @@ static void gl847_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
     // compute pixel coordinate in the given dpihw space, taking segments into account
     startx /= factor*segnb;
     endx /= factor*segnb;
-  dev->len=endx-startx;
+    dev->deseg.pixel_groups = endx-startx;
     dev->deseg.conseq_pixel_dist_bytes = 0;
   dev->skip=0;
 
@@ -891,7 +891,7 @@ static void gl847_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   /* words(16bit) before gamma, conversion to 8 bit or lineart*/
     dev->deseg.raw_channel_bytes = multiply_by_depth_ceil((used_pixels * dpiset) / dpihw,
                                                           session.params.depth);
-    dev->len = multiply_by_depth_ceil(dev->len, session.params.depth);
+    dev->deseg.pixel_groups = multiply_by_depth_ceil(dev->deseg.pixel_groups, session.params.depth);
     dev->deseg.conseq_pixel_dist_bytes = multiply_by_depth_ceil(dev->deseg.conseq_pixel_dist_bytes, session.params.depth);
 
   dev->cur=0;
@@ -910,7 +910,7 @@ static void gl847_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG (DBG_io2, "%s: pixels     =%d\n", __func__, session.optical_pixels);
   DBG (DBG_io2, "%s: depth      =%d\n", __func__, session.params.depth);
   DBG (DBG_io2, "%s: dev->bpl   =%lu\n", __func__, (unsigned long) dev->deseg.raw_channel_bytes);
-  DBG (DBG_io2, "%s: dev->len   =%lu\n", __func__, (unsigned long)dev->len);
+  DBG (DBG_io2, "%s: dev->len   =%lu\n", __func__, (unsigned long) dev->deseg.pixel_groups);
   DBG (DBG_io2, "%s: dev->dist  =%lu\n", __func__, (unsigned long) dev->deseg.conseq_pixel_dist_bytes);
   DBG (DBG_io2, "%s: dev->segnb =%lu\n", __func__, (unsigned long)dev->segnb);