X-Git-Url: https://git.openssl.org/?p=openssl.git;a=blobdiff_plain;f=doc%2Fman3%2FEVP_MAC.pod;h=a55d8db259c099afde36ba441bfa63c98c68f521;hp=32bf5896f804e7d981170d5bd4af6790c584cb0e;hb=48fdeca01dab31237a711d9fdf4452ebf8443716;hpb=17838470617afd50813a66adcebad2e6e17de79c

diff --git a/doc/man3/EVP_MAC.pod b/doc/man3/EVP_MAC.pod
index 32bf5896f8..a55d8db259 100644
--- a/doc/man3/EVP_MAC.pod
+++ b/doc/man3/EVP_MAC.pod
@@ -202,6 +202,9 @@ For MAC implementations that use an underlying computation algorithm,
 these controls set what the algorithm should be, and the engine that
 implements the algorithm if needed.
 
+Note that not all algorithms may support all digests. HMAC does not support
+variable output length digests such as SHAKE128 or SHAKE256.
+
 B<EVP_MAC_CTRL_SET_ENGINE> takes one argument: C<ENGINE *>
 
 B<EVP_MAC_CTRL_SET_MD> takes one argument: C<EVP_MD *>