diff --git a/src/secp256k1/src/ecmult.h b/src/secp256k1/src/ecmult.h
index fbcf6a445..3ed2e435a 100644
--- a/src/secp256k1/src/ecmult.h
+++ b/src/secp256k1/src/ecmult.h
@@ -78,6 +78,10 @@ typedef int (secp256k1_ecmult_multi_callback)(secp256k1_scalar *sc, secp256k1_ge
  *          0 if there is not enough scratch space for a single point or
  *          callback returns 0
  */
+
+#ifdef __cplusplus
+extern "C"
+#endif
 int secp256k1_ecmult_multi_var(const secp256k1_ecmult_context *ctx, secp256k1_scratch *scratch, secp256k1_gej *r, const secp256k1_scalar *inp_g_sc, secp256k1_ecmult_multi_callback cb, void *cbdata, size_t n);
 
 #endif /* SECP256K1_ECMULT_H */