diff --git a/src/modules/aggsig/main_impl.h b/src/modules/aggsig/main_impl.h
index 0af253c..3d8fa65 100644
--- a/src/modules/aggsig/main_impl.h
+++ b/src/modules/aggsig/main_impl.h
@@ -37,14 +37,16 @@ static int secp256k1_compute_sighash_single(const secp256k1_context *ctx, secp25
     unsigned char output[32];
     unsigned char buf[33];
     size_t buflen = sizeof(buf);
-
     int overflow;
+
     secp256k1_sha256 hasher;
     secp256k1_sha256_initialize(&hasher);
 
     /* Encode public nonce */
     CHECK(secp256k1_ec_pubkey_serialize(ctx, buf, &buflen, pubkey, SECP256K1_EC_COMPRESSED));
-    secp256k1_sha256_write(&hasher, buf, sizeof(buf));
+
+    /* Remove the first encoding element, as it may differ depending on how we got here */
+    secp256k1_sha256_write(&hasher, buf+1, sizeof(buf-1));
 
     /* Encode message */
     secp256k1_sha256_write(&hasher, msghash32, 32);
diff --git a/src/modules/aggsig/tests_impl.h b/src/modules/aggsig/tests_impl.h
index 00543dd..51af094 100644
--- a/src/modules/aggsig/tests_impl.h
+++ b/src/modules/aggsig/tests_impl.h
@@ -199,7 +199,6 @@ void test_aggsig_api(void) {
 
         /* Receiver verifies sender's Sig and signs */
         CHECK(secp256k1_aggsig_verify_single(vrfy, sig, msg, &combiner_sum, &pubkeys[0], 1));
-
         CHECK(secp256k1_aggsig_sign_single(sign, sig2, msg, seckeys[1], sec_nonces[1], &combiner_sum, &combiner_sum, seed));
         /* sender verifies receiver's Sig then creates final combined sig */
         CHECK(secp256k1_aggsig_verify_single(vrfy, sig2, msg, &combiner_sum, &pubkeys[1], 1));
@@ -212,12 +211,17 @@ void test_aggsig_api(void) {
         pubkey_combiner[1]=&pubkeys[1];
         CHECK(secp256k1_ec_pubkey_combine(ctx, &combiner_sum_2, pubkey_combiner, 2) == 1);
 
-        /* Ensure added sigs verify properly */
+        /* Ensure added sigs verify properly (with and without providing nonce_sum */
         CHECK(secp256k1_aggsig_verify_single(vrfy, combined_sig, msg, &combiner_sum, &combiner_sum_2, 0));
+        CHECK(secp256k1_aggsig_verify_single(vrfy, combined_sig, msg, NULL, &combiner_sum_2, 0));
 
         /* And anything else doesnt' */
         CHECK(!secp256k1_aggsig_verify_single(vrfy, combined_sig, msg, &pub_nonces[0], &combiner_sum_2, 0));
-        CHECK(!secp256k1_aggsig_verify_single(vrfy, combined_sig, msg, &combiner_sum, &pub_nonces[1], 0));
+        CHECK(!secp256k1_aggsig_verify_single(vrfy, combined_sig, msg, NULL, &pub_nonces[1], 0));
+        msg[0]=1;
+        msg[1]=2;
+        msg[2]=3;
+        CHECK(!secp256k1_aggsig_verify_single(vrfy, combined_sig, msg, NULL, &combiner_sum_2, 0));
 
     }
     /*** End aggsig for Grin exchange test ***/