diff --git a/src/modules/schnorrsig/main_impl.h b/src/modules/schnorrsig/main_impl.h
index 8b215538fd..3650e7c77b 100644
--- a/src/modules/schnorrsig/main_impl.h
+++ b/src/modules/schnorrsig/main_impl.h
@@ -122,7 +122,7 @@ static void secp256k1_schnorrsig_challenge(secp256k1_scalar* e, const unsigned c
     secp256k1_scalar_set_b32(e, buf, NULL);
 }
 
-int secp256k1_schnorrsig_sign_internal(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char *msg, size_t msglen, const secp256k1_keypair *keypair, secp256k1_nonce_function_hardened noncefp, void *ndata) {
+static int secp256k1_schnorrsig_sign_internal(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char *msg, size_t msglen, const secp256k1_keypair *keypair, secp256k1_nonce_function_hardened noncefp, void *ndata) {
     secp256k1_scalar sk;
     secp256k1_scalar e;
     secp256k1_scalar k;