diff --git a/include/secp256k1_musig.h b/include/secp256k1_musig.h
index a064ed33d..3aba53a33 100644
--- a/include/secp256k1_musig.h
+++ b/include/secp256k1_musig.h
@@ -234,7 +234,7 @@ SECP256K1_API int secp256k1_musig_pubkey_agg(
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_pubkey_get(
     const secp256k1_context *ctx,
     secp256k1_pubkey *agg_pk,
-    secp256k1_musig_keyagg_cache *keyagg_cache
+    const secp256k1_musig_keyagg_cache *keyagg_cache
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Apply plain "EC" tweaking to a public key in a given keyagg_cache by
diff --git a/src/modules/musig/keyagg_impl.h b/src/modules/musig/keyagg_impl.h
index aeb942ac8..95da286ff 100644
--- a/src/modules/musig/keyagg_impl.h
+++ b/src/modules/musig/keyagg_impl.h
@@ -278,7 +278,7 @@ int secp256k1_musig_pubkey_agg(const secp256k1_context* ctx, secp256k1_scratch_s
     return 1;
 }
 
-int secp256k1_musig_pubkey_get(const secp256k1_context* ctx, secp256k1_pubkey *agg_pk, secp256k1_musig_keyagg_cache *keyagg_cache) {
+int secp256k1_musig_pubkey_get(const secp256k1_context* ctx, secp256k1_pubkey *agg_pk, const secp256k1_musig_keyagg_cache *keyagg_cache) {
     secp256k1_keyagg_cache_internal cache_i;
     VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(agg_pk != NULL);