diff --git a/README.md b/README.md
index 32dbab4..7df891d 100644
--- a/README.md
+++ b/README.md
@@ -46,4 +46,8 @@ Restore to null.null to use bundleid included in the ipa.
 Using a custom bundleid, if the ipa includes additional apps (for example widget and apple watch), the script will automatically change these bundleids using the following convention : custombundleid.extra1, custombundleid.extra2 and so on.
 
 If you want to change a bundleid for a particular ipa, use only that ipa in the source folder otherwise all ipas present in the source folder will be signed using the same bundleid.
+
+OSX Sierra can output some error during signing.
+security: SecPolicySetValue: One or more parameters passed to a function were not valid.
+This error maybe is related to some changes by Apple. Ignore it, the signing process is fine.
 ```
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