diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index a772094..57053ef 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3022,8 +3022,7 @@
     if( PSA_ALG_IS_HMAC( alg ) )
     {
         /* Sanity check. This shouldn't fail on a valid configuration. */
-        if( operation->mac_size == 0 ||
-            operation->mac_size > sizeof( operation->ctx.hmac.opad ) )
+        if( operation->mac_size > sizeof( operation->ctx.hmac.opad ) )
         {
             status = PSA_ERROR_NOT_SUPPORTED;
             goto exit;