diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 6865a5d..8941f89 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1048,9 +1048,16 @@
   def WriteScript(self, script, output_zip, progress=None):
     if not self.src:
       # write the output unconditionally
-      if progress: script.ShowProgress(progress, 0)
-      self._WriteUpdate(script, output_zip)
+      script.Print("Patching %s image unconditionally..." % (self.partition,))
+    else:
+      script.Print("Patching %s image after verification." % (self.partition,))
 
+    if progress: script.ShowProgress(progress, 0)
+    self._WriteUpdate(script, output_zip)
+
+  def WriteVerifyScript(self, script):
+    if not self.src:
+      script.Print("Image %s will be patched unconditionally." % (self.partition,))
     else:
       if self.check_first_block:
         self._CheckFirstBlock(script)
@@ -1058,9 +1065,7 @@
       script.AppendExtra('if range_sha1("%s", "%s") == "%s" then' %
                          (self.device, self.src.care_map.to_string_raw(),
                           self.src.TotalSha1()))
-      script.Print("Patching %s image..." % (self.partition,))
-      if progress: script.ShowProgress(progress, 0)
-      self._WriteUpdate(script, output_zip)
+      script.Print("Verified %s image..." % (self.partition,))
       script.AppendExtra(('else\n'
                           '  (range_sha1("%s", "%s") == "%s") ||\n'
                           '  abort("%s partition has unexpected contents");\n'
diff --git a/tools/releasetools/ota_from_target_files b/tools/releasetools/ota_from_target_files
index 755e5c2..945f11a 100755
--- a/tools/releasetools/ota_from_target_files
+++ b/tools/releasetools/ota_from_target_files
@@ -558,6 +558,7 @@
 
   system_items = ItemSet("system", "META/filesystem_config.txt")
   script.ShowProgress(system_progress, 0)
+
   if block_based:
     # Full OTA is done as an "incremental" against an empty source
     # image.  This has the effect of writing new data from the package
@@ -845,6 +846,11 @@
 else
 """ % bcb_dev)
 
+  # Verify the existing partitions.
+  system_diff.WriteVerifyScript(script)
+  if vendor_diff:
+    vendor_diff.WriteVerifyScript(script)
+
   script.Comment("---- start making changes here ----")
 
   device_specific.IncrementalOTA_InstallBegin()