diff --git a/src/modules/schnorrsig/tests_impl.h b/src/modules/schnorrsig/tests_impl.h
index adb4d7258..106219b42 100644
--- a/src/modules/schnorrsig/tests_impl.h
+++ b/src/modules/schnorrsig/tests_impl.h
@@ -1132,6 +1132,7 @@ static void test_schnorrsig_aggregate_api(void) {
     unsigned char sigs64[N*64];
     unsigned char aggsig[32*(N + 1)];
     size_t aggsig_size = 32*(N + 1);
+    size_t size_max = (size_t) - 1;
     int i;
     for (i = 0; i < N; ++i) {
         unsigned char sk[32];
@@ -1163,8 +1164,8 @@ static void test_schnorrsig_aggregate_api(void) {
     CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, NULL, msgs32, &sigs64[N_INITIAL*64], N_INITIAL, N_NEW));
     CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, NULL, &sigs64[N_INITIAL*64], N_INITIAL, N_NEW));
     CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, msgs32, NULL, N_INITIAL, N_NEW));
-    CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, msgs32, &sigs64[N_INITIAL*64], __SIZE_MAX__, N_NEW));
-    CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, msgs32, &sigs64[N_INITIAL*64], N_INITIAL, __SIZE_MAX__));
+    CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, msgs32, &sigs64[N_INITIAL*64], size_max, size_max));
+    CHECK_ILLEGAL(CTX, secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, msgs32, &sigs64[N_INITIAL*64], N_INITIAL, size_max));
     aggsig_size = 32*N;
     CHECK(secp256k1_schnorrsig_inc_aggregate(CTX, aggsig, &aggsig_size, pubkeys, msgs32, &sigs64[N_INITIAL*64], N_INITIAL, N_NEW) == 0);
     aggsig_size = 32*(N+1)-1;