diff --git a/jcapistd.c b/jcapistd.c
index c0320b1b..a0dbf8be 100644
--- a/jcapistd.c
+++ b/jcapistd.c
@@ -3,6 +3,8 @@
  *
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * This file is part of the Independent JPEG Group's software.
+ * mozjpeg Modifications:
+ * Copyright (C) 2014, Mozilla Corporation.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains application interface code for the compression half
@@ -43,6 +45,10 @@ jpeg_start_compress (j_compress_ptr cinfo, boolean write_all_tables)
   if (write_all_tables)
     jpeg_suppress_tables(cinfo, FALSE);	/* mark all tables to be written */
 
+  /* setting up scan optimisation pattern failed, disable scan optimisation */
+  if (cinfo->num_scans_luma == 0)
+    cinfo->optimize_scans = FALSE;
+  
   /* (Re)initialize error mgr and destination modules */
   (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
   (*cinfo->dest->init_destination) (cinfo);
diff --git a/jcmaster.c b/jcmaster.c
index 47d7387e..1f7b80f6 100644
--- a/jcmaster.c
+++ b/jcmaster.c
@@ -644,92 +644,95 @@ select_scans (j_compress_ptr cinfo, int next_scan_number)
     for (i = 0; i < cinfo->num_scans_luma; i++)
       free(cinfo->scan_buffer[i]);
     
-  } else if (next_scan_number == cinfo->num_scans_luma+cinfo->num_scans_chroma_dc) {
-    base_scan_idx = cinfo->num_scans_luma;
+  } else if (cinfo->num_scans > cinfo->num_scans_luma) {
     
-    if (cinfo->scan_size[base_scan_idx] <= cinfo->scan_size[base_scan_idx+1] + cinfo->scan_size[base_scan_idx+2])
-      copy_buffer(cinfo, base_scan_idx);
-    else {
-      copy_buffer(cinfo, base_scan_idx+1);
-      copy_buffer(cinfo, base_scan_idx+2);
-    }
-    
-  } else if (next_scan_number == cinfo->num_scans_luma+cinfo->num_scans_chroma_dc+(6*cinfo->Al_max_chroma+4)) {
-    int Al;
-    int i;
-    base_scan_idx = cinfo->num_scans_luma + cinfo->num_scans_chroma_dc;
-    cinfo->best_Al = 0;
-    
-    for (Al = 0; Al <= cinfo->Al_max_chroma; Al++) {
-      size[Al]  = cinfo->scan_size[base_scan_idx + 0 + 4 * Al];
-      size[Al] += cinfo->scan_size[base_scan_idx + 1 + 4 * Al];
-      size[Al] += cinfo->scan_size[base_scan_idx + 2 + 4 * Al];
-      size[Al] += cinfo->scan_size[base_scan_idx + 3 + 4 * Al];
+    if (next_scan_number == cinfo->num_scans_luma+cinfo->num_scans_chroma_dc) {
+      base_scan_idx = cinfo->num_scans_luma;
       
-      for (i = 0; i < Al; i++) {
-        size[Al] += cinfo->scan_size[base_scan_idx + 4 + 4*cinfo->Al_max_chroma + 2*i];
-        size[Al] += cinfo->scan_size[base_scan_idx + 5 + 4*cinfo->Al_max_chroma + 2*i];
+      if (cinfo->scan_size[base_scan_idx] <= cinfo->scan_size[base_scan_idx+1] + cinfo->scan_size[base_scan_idx+2])
+        copy_buffer(cinfo, base_scan_idx);
+      else {
+        copy_buffer(cinfo, base_scan_idx+1);
+        copy_buffer(cinfo, base_scan_idx+2);
       }
       
-      if (size[Al] < size[cinfo->best_Al])
-        cinfo->best_Al = Al;
-    }
-    
-    jpeg_scan_info *scanptr = (jpeg_scan_info *)&cinfo->scan_info[next_scan_number];
-    
-    for (i = 0; i < 4*cinfo->num_frequency_splits+2; i++)
-      scanptr[i].Al = cinfo->best_Al;
-    
-  } else if (next_scan_number == cinfo->num_scans) {
-    int Al;
-    int i;
-    base_scan_idx = next_scan_number - (4*cinfo->num_frequency_splits+2);
-    
-    size[0]  = cinfo->scan_size[base_scan_idx];
-    size[0] += cinfo->scan_size[base_scan_idx+1];
-    for (i = 0; i < cinfo->num_frequency_splits; i++) {
-      size[i+1]  = cinfo->scan_size[base_scan_idx+0+4*i] + cinfo->scan_size[base_scan_idx+1+4*i];
-      size[i+1] += cinfo->scan_size[base_scan_idx+2+4*i] + cinfo->scan_size[base_scan_idx+3+4*i];
-    }
-    
-    int best = 0;
-    if (size[1] < size[best])
-      best = 1;
-    if (size[2] < size[best])
-      best = 2;
-    if (best != 0) {
-      if (size[3] < size[best])
-        best = 3;
-      if (best == 2) {
-        if (size[4] < size[best]) {
-          best = 4;
-          if (size[5] < size[best])
-            best = 5;
+    } else if (next_scan_number == cinfo->num_scans_luma+cinfo->num_scans_chroma_dc+(6*cinfo->Al_max_chroma+4)) {
+      int Al;
+      int i;
+      base_scan_idx = cinfo->num_scans_luma + cinfo->num_scans_chroma_dc;
+      cinfo->best_Al = 0;
+      
+      for (Al = 0; Al <= cinfo->Al_max_chroma; Al++) {
+        size[Al]  = cinfo->scan_size[base_scan_idx + 0 + 4 * Al];
+        size[Al] += cinfo->scan_size[base_scan_idx + 1 + 4 * Al];
+        size[Al] += cinfo->scan_size[base_scan_idx + 2 + 4 * Al];
+        size[Al] += cinfo->scan_size[base_scan_idx + 3 + 4 * Al];
+        
+        for (i = 0; i < Al; i++) {
+          size[Al] += cinfo->scan_size[base_scan_idx + 4 + 4*cinfo->Al_max_chroma + 2*i];
+          size[Al] += cinfo->scan_size[base_scan_idx + 5 + 4*cinfo->Al_max_chroma + 2*i];
+        }
+        
+        if (size[Al] < size[cinfo->best_Al])
+          cinfo->best_Al = Al;
+      }
+      
+      jpeg_scan_info *scanptr = (jpeg_scan_info *)&cinfo->scan_info[next_scan_number];
+      
+      for (i = 0; i < 4*cinfo->num_frequency_splits+2; i++)
+        scanptr[i].Al = cinfo->best_Al;
+      
+    } else if (next_scan_number == cinfo->num_scans) {
+      int Al;
+      int i;
+      base_scan_idx = next_scan_number - (4*cinfo->num_frequency_splits+2);
+      
+      size[0]  = cinfo->scan_size[base_scan_idx];
+      size[0] += cinfo->scan_size[base_scan_idx+1];
+      for (i = 0; i < cinfo->num_frequency_splits; i++) {
+        size[i+1]  = cinfo->scan_size[base_scan_idx+0+4*i] + cinfo->scan_size[base_scan_idx+1+4*i];
+        size[i+1] += cinfo->scan_size[base_scan_idx+2+4*i] + cinfo->scan_size[base_scan_idx+3+4*i];
+      }
+      
+      int best = 0;
+      if (size[1] < size[best])
+        best = 1;
+      if (size[2] < size[best])
+        best = 2;
+      if (best != 0) {
+        if (size[3] < size[best])
+          best = 3;
+        if (best == 2) {
+          if (size[4] < size[best]) {
+            best = 4;
+            if (size[5] < size[best])
+              best = 5;
+          }
         }
       }
+      
+      if (best == 0) {
+        copy_buffer(cinfo, base_scan_idx);
+        copy_buffer(cinfo, base_scan_idx+1);
+      }
+      else {
+        copy_buffer(cinfo, base_scan_idx-2+4*best);
+        copy_buffer(cinfo, base_scan_idx-1+4*best);
+        copy_buffer(cinfo, base_scan_idx+0+4*best);
+        copy_buffer(cinfo, base_scan_idx-1+4*best);
+      }
+      
+      base_scan_idx = cinfo->num_scans_luma + cinfo->num_scans_chroma_dc;
+      
+      for (Al = cinfo->best_Al-1; Al >= 0; Al--) {
+        copy_buffer(cinfo, base_scan_idx + 4*(cinfo->Al_max_chroma+1) + 2*Al + 0);
+        copy_buffer(cinfo, base_scan_idx + 4*(cinfo->Al_max_chroma+1) + 2*Al + 1);
+      }
+      
+      /* free the memory allocated for the chroma buffers */
+      for (i = cinfo->num_scans_luma; i < cinfo->num_scans; i++)
+        free(cinfo->scan_buffer[i]);
     }
-    
-    if (best == 0) {
-      copy_buffer(cinfo, base_scan_idx);
-      copy_buffer(cinfo, base_scan_idx+1);
-    }
-    else {
-      copy_buffer(cinfo, base_scan_idx-2+4*best);
-      copy_buffer(cinfo, base_scan_idx-1+4*best);
-      copy_buffer(cinfo, base_scan_idx+0+4*best);
-      copy_buffer(cinfo, base_scan_idx-1+4*best);
-    }
-    
-    base_scan_idx = cinfo->num_scans_luma + cinfo->num_scans_chroma_dc;
-    
-    for (Al = cinfo->best_Al-1; Al >= 0; Al--) {
-      copy_buffer(cinfo, base_scan_idx + 4*(cinfo->Al_max_chroma+1) + 2*Al + 0);
-      copy_buffer(cinfo, base_scan_idx + 4*(cinfo->Al_max_chroma+1) + 2*Al + 1);
-    }
-    
-    /* free the memory allocated for the chroma buffers */
-    for (i = cinfo->num_scans_luma; i < cinfo->num_scans; i++)
-      free(cinfo->scan_buffer[i]);
   }
 }
 
diff --git a/jcparam.c b/jcparam.c
index 781679f2..4621c979 100644
--- a/jcparam.c
+++ b/jcparam.c
@@ -612,12 +612,15 @@ fill_dc_scans (jpeg_scan_info * scanptr, int ncomps, int Ah, int Al)
  * cinfo->num_components and cinfo->jpeg_color_space must be correct.
  */
 
-LOCAL(void)
+LOCAL(boolean)
 jpeg_search_progression (j_compress_ptr cinfo)
 {
   int ncomps = cinfo->num_components;
   int nscans;
   jpeg_scan_info * scanptr;
+  int Al;
+  int frequency_split[] = { 2, 8, 5, 12, 18 };
+  int i;
   
   /* Safety check to ensure start_compress not called yet. */
   if (cinfo->global_state != CSTATE_START)
@@ -627,19 +630,11 @@ jpeg_search_progression (j_compress_ptr cinfo)
   if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {
     /* Custom script for YCbCr color images. */
     nscans = 64;
+  } else if (ncomps == 1) {
+    nscans = 23;
   } else {
-    /* All-purpose script for other color spaces. */
-    if (cinfo->use_moz_defaults) {
-      if (ncomps > MAX_COMPS_IN_SCAN)
-        nscans = 5 * ncomps;	/* 2 DC + 4 AC scans per component */
-      else
-        nscans = 1 + 4 * ncomps;	/* 2 DC scans; 4 AC scans per component */
-    } else {
-      if (ncomps > MAX_COMPS_IN_SCAN)
-        nscans = 6 * ncomps;	/* 2 DC + 4 AC scans per component */
-      else
-        nscans = 2 + 4 * ncomps;	/* 2 DC scans; 4 AC scans per component */
-    }
+    cinfo->num_scans_luma = 0;
+    return FALSE;
   }
   
   /* Allocate space for script.
@@ -650,7 +645,7 @@ jpeg_search_progression (j_compress_ptr cinfo)
    * enough space to handle YCbCr even if initially asked for grayscale.
    */
   if (cinfo->script_space == NULL || cinfo->script_space_size < nscans) {
-    cinfo->script_space_size = MAX(nscans, 10);
+    cinfo->script_space_size = MAX(nscans, 64);
     cinfo->script_space = (jpeg_scan_info *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                                 cinfo->script_space_size * SIZEOF(jpeg_scan_info));
@@ -659,44 +654,43 @@ jpeg_search_progression (j_compress_ptr cinfo)
   cinfo->scan_info = scanptr;
   cinfo->num_scans = nscans;
   
-  if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {
-    int Al;
-    int frequency_split[] = { 2, 8, 5, 12, 18 };
-    int i;
-    
-    cinfo->Al_max_luma = 3;
+  cinfo->Al_max_luma = 3;
+  cinfo->num_scans_luma_dc = 1;
+  cinfo->num_frequency_splits = 5;
+  cinfo->num_scans_luma = cinfo->num_scans_luma_dc + (3 * cinfo->Al_max_luma + 2) + (2 * cinfo->num_frequency_splits + 1);
+  
+  /* 23 scans for luma */
+  /* 1 scan for DC */
+  /* 11 scans to determine successive approximation */
+  /* 11 scans to determine frequency approximation */
+  /* after 12 scans need to update following 11 */
+  /* after 23 scans need to determine which to keep */
+  /* last 4 done conditionally */
+  
+  /* luma DC by itself */
+  scanptr = fill_dc_scans(scanptr, 1, 0, 0);
+  
+  for (Al = 0; Al <= cinfo->Al_max_luma; Al++) {
+    scanptr = fill_a_scan(scanptr, 0, 1, 8, 0, Al);
+    scanptr = fill_a_scan(scanptr, 0, 9, 63, 0, Al);
+  }
+  
+  for (Al = 0; Al < cinfo->Al_max_luma; Al++)
+    scanptr = fill_a_scan(scanptr, 0, 1, 63, Al+1, Al);
+  
+  scanptr = fill_a_scan(scanptr, 0, 1, 63, 0, 0);
+  
+  for (i = 0; i < cinfo->num_frequency_splits; i++) {
+    scanptr = fill_a_scan(scanptr, 0, 1, frequency_split[i], 0, 0);
+    scanptr = fill_a_scan(scanptr, 0, frequency_split[i]+1, 63, 0, 0);
+  }
+  
+  if (ncomps == 1) {
+    cinfo->Al_max_chroma = 0;
+    cinfo->num_scans_chroma_dc = 0;
+  } else {
     cinfo->Al_max_chroma = 2;
-    cinfo->num_scans_luma_dc = 1;
     cinfo->num_scans_chroma_dc = 3;
-    cinfo->num_frequency_splits = 5;
-    cinfo->num_scans_luma = cinfo->num_scans_luma_dc + (3 * cinfo->Al_max_luma + 2) + (2 * cinfo->num_frequency_splits + 1);
-    
-    /* 23 scans for luma */
-    /* 1 scan for DC */
-    /* 11 scans to determine successive approximation */
-    /* 11 scans to determine frequency approximation */
-    /* after 12 scans need to update following 11 */
-    /* after 23 scans need to determine which to keep */
-    /* last 4 done conditionally */
-    
-    /* luma DC by itself */
-    scanptr = fill_dc_scans(scanptr, 1, 0, 0);
-    
-    for (Al = 0; Al <= cinfo->Al_max_luma; Al++) {
-      scanptr = fill_a_scan(scanptr, 0, 1, 8, 0, Al);
-      scanptr = fill_a_scan(scanptr, 0, 9, 63, 0, Al);
-    }
-    
-    for (Al = 0; Al < cinfo->Al_max_luma; Al++)
-      scanptr = fill_a_scan(scanptr, 0, 1, 63, Al+1, Al);
-    
-    scanptr = fill_a_scan(scanptr, 0, 1, 63, 0, 0);
-    
-    for (i = 0; i < cinfo->num_frequency_splits; i++) {
-      scanptr = fill_a_scan(scanptr, 0, 1, frequency_split[i], 0, 0);
-      scanptr = fill_a_scan(scanptr, 0, frequency_split[i]+1, 63, 0, 0);
-    }
-    
     /* 41 scans for chroma */
     
     /* chroma DC combined */
@@ -726,9 +720,9 @@ jpeg_search_progression (j_compress_ptr cinfo)
       scanptr = fill_a_scan(scanptr, 2, 1, frequency_split[i], 0, 0);
       scanptr = fill_a_scan(scanptr, 2, frequency_split[i]+1, 63, 0, 0);
     }
-  } else {
-    /* TODO */
   }
+  
+  return TRUE;
 }
 
 /*
@@ -740,9 +734,10 @@ GLOBAL(void)
 jpeg_simple_progression (j_compress_ptr cinfo)
 {
   if (cinfo->optimize_scans) {
-    jpeg_search_progression(cinfo);
-    return;
+    if (jpeg_search_progression(cinfo) == TRUE)
+      return;
   }
+  
   int ncomps = cinfo->num_components;
   int nscans;
   jpeg_scan_info * scanptr;