diff -up openssl-3.0.0-alpha16/apps/dgst.c.digest openssl-3.0.0-alpha16/apps/dgst.c
--- openssl-3.0.0-alpha16/apps/dgst.c.digest	2021-06-04 10:21:03.153697643 +0200
+++ openssl-3.0.0-alpha16/apps/dgst.c	2021-06-04 10:22:26.737489944 +0200
@@ -330,6 +330,8 @@ int dgst_main(int argc, char **argv)
     }
 
     if (hmac_key != NULL) {
+        if (md == NULL)
+            md = (EVP_MD *)EVP_sha256();
         sigkey = EVP_PKEY_new_raw_private_key(EVP_PKEY_HMAC, impl,
                                               (unsigned char *)hmac_key,
                                               strlen(hmac_key));
diff -up openssl-3.0.0-alpha16/test/recipes/20-test_dgst.t.digest openssl-3.0.0-alpha16/test/recipes/20-test_dgst.t
--- openssl-3.0.0-alpha16/test/recipes/20-test_dgst.t.digest	2021-06-04 10:21:18.871846631 +0200
+++ openssl-3.0.0-alpha16/test/recipes/20-test_dgst.t	2021-06-04 10:23:56.862344245 +0200
@@ -17,7 +17,7 @@ use OpenSSL::Test::Utils;
 
 setup("test_dgst");
 
-plan tests => 7;
+plan tests => 8;
 
 sub tsignverify {
     my $testtext = shift;
@@ -115,6 +115,20 @@ subtest "HMAC generation with `dgst` CLI
     ok($hmacdata[0] =~ $expected, "HMAC: Check HMAC value is as expected ($hmacdata[0]) vs ($expected)");
     ok($hmacdata[1] =~ $expected,
        "HMAC: Check second HMAC value is consistent with the first ($hmacdata[1]) vs ($expected)");
+};
+
+subtest "HMAC generation with `dgst` CLI, default digest" => sub {
+    plan tests => 2;
+
+    my $testdata = srctop_file('test', 'data.bin');
+    #HMAC the data twice to check consistency
+    my @hmacdata = run(app(['openssl', 'dgst', '-hmac', '123456',
+                            $testdata, $testdata]), capture => 1);
+    chomp(@hmacdata);
+    my $expected = qr/HMAC-SHA256\(\Q$testdata\E\)= 6f12484129c4a761747f13d8234a1ff0e074adb34e9e9bf3a155c391b97b9a7c/;
+    ok($hmacdata[0] =~ $expected, "HMAC: Check HMAC value is as expected ($hmacdata[0]) vs ($expected)");
+    ok($hmacdata[1] =~ $expected,
+       "HMAC: Check second HMAC value is consistent with the first ($hmacdata[1]) vs ($expected)");
 };
 
 subtest "Custom length XOF digest generation with `dgst` CLI" => sub {