diff --git a/doc/arm/pkcs11.rst b/doc/arm/pkcs11.rst
index 5132a3b229..07a59dafbc 100644
--- a/doc/arm/pkcs11.rst
+++ b/doc/arm/pkcs11.rst
@@ -113,7 +113,9 @@ brackets) are defined:
 
    openssl_conf = openssl_init
 
-And add following lines at the bottom of the file:
+And make sure there are no other 'openssl_conf = ...' lines in the file.
+
+Add following lines at the bottom of the file:
 
 ::