diff --git a/thicken-manifests.py b/thicken-manifests.py
index 17a19e3..0e46f04 100755
--- a/thicken-manifests.py
+++ b/thicken-manifests.py
@@ -126,6 +126,10 @@ def maybe_thicken_manifest(pkg_dir):
 		return
 	# If it changed, write it out
 	if manifest.write():
+		if newest_mtime == manifest_mtime:
+			# portage says the manifest changed, but mtime is supposed to stay the same
+			# bump the mtime by 1 to be safe
+			newest_mtime += 1
 		if args.sign:
 			try:
 				gpg_sign(manifest.getFullname())