diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 15964b1..50ef451 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -900,10 +900,26 @@
       cmd.append(ttemp.name)
       cmd.append(ptemp.name)
       p = Run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-      _, err = p.communicate()
+      err = []
+      def run():
+        _, e = p.communicate()
+        if e: err.append(e)
+      th = threading.Thread(target=run)
+      th.start()
+      th.join(timeout=300)   # 5 mins
+      if th.is_alive():
+        print "WARNING: diff command timed out"
+        p.terminate()
+        th.join(5)
+        if th.is_alive():
+          p.kill()
+          th.join()
+
       if err or p.returncode != 0:
-        print "WARNING: failure running %s:\n%s\n" % (diff_program, err)
-        return None
+        print "WARNING: failure running %s:\n%s\n" % (
+            diff_program, "".join(err))
+        self.patch = None
+        return None, None, None
       diff = ptemp.read()
     finally:
       ptemp.close()
diff --git a/tools/releasetools/ota_from_target_files b/tools/releasetools/ota_from_target_files
index f848fd5..9f70167 100755
--- a/tools/releasetools/ota_from_target_files
+++ b/tools/releasetools/ota_from_target_files
@@ -853,19 +853,24 @@
         GetBuildProp("ro.build.thumbprint", OPTIONS.source_info_dict))
 
   if updating_boot:
+    boot_type, boot_device = common.GetTypeAndDevice("/boot", OPTIONS.info_dict)
     d = common.Difference(target_boot, source_boot)
     _, _, d = d.ComputePatch()
-    print "boot      target: %d  source: %d  diff: %d" % (
-        target_boot.size, source_boot.size, len(d))
+    if d is None:
+      include_full_boot = True
+      common.ZipWriteStr(output_zip, "boot.img", target_boot.data)
+    else:
+      include_full_boot = False
 
-    common.ZipWriteStr(output_zip, "patch/boot.img.p", d)
+      print "boot      target: %d  source: %d  diff: %d" % (
+          target_boot.size, source_boot.size, len(d))
 
-    boot_type, boot_device = common.GetTypeAndDevice("/boot", OPTIONS.info_dict)
+      common.ZipWriteStr(output_zip, "patch/boot.img.p", d)
 
-    script.PatchCheck("%s:%s:%d:%s:%d:%s" %
-                      (boot_type, boot_device,
-                       source_boot.size, source_boot.sha1,
-                       target_boot.size, target_boot.sha1))
+      script.PatchCheck("%s:%s:%d:%s:%d:%s" %
+                        (boot_type, boot_device,
+                         source_boot.size, source_boot.sha1,
+                         target_boot.size, target_boot.sha1))
 
   device_specific.IncrementalOTA_VerifyEnd()
 
@@ -906,19 +911,24 @@
 
   if not OPTIONS.two_step:
     if updating_boot:
-      # Produce the boot image by applying a patch to the current
-      # contents of the boot partition, and write it back to the
-      # partition.
-      script.Print("Patching boot image...")
-      script.ShowProgress(0.1, 10)
-      script.ApplyPatch("%s:%s:%d:%s:%d:%s"
-                        % (boot_type, boot_device,
-                           source_boot.size, source_boot.sha1,
-                           target_boot.size, target_boot.sha1),
-                        "-",
-                        target_boot.size, target_boot.sha1,
-                        source_boot.sha1, "patch/boot.img.p")
-      print "boot image changed; including."
+      if include_full_boot:
+        print "boot image changed; including full."
+        script.Print("Installing boot image...")
+        script.WriteRawImage("/boot", "boot.img")
+      else:
+        # Produce the boot image by applying a patch to the current
+        # contents of the boot partition, and write it back to the
+        # partition.
+        print "boot image changed; including patch."
+        script.Print("Patching boot image...")
+        script.ShowProgress(0.1, 10)
+        script.ApplyPatch("%s:%s:%d:%s:%d:%s"
+                          % (boot_type, boot_device,
+                             source_boot.size, source_boot.sha1,
+                             target_boot.size, target_boot.sha1),
+                          "-",
+                          target_boot.size, target_boot.sha1,
+                          source_boot.sha1, "patch/boot.img.p")
     else:
       print "boot image unchanged; skipping."