diff --git a/src/secp256k1/src/ecmult_const.h b/src/secp256k1/src/ecmult_const.h
index 72bf7d758..0d32fa389 100644
--- a/src/secp256k1/src/ecmult_const.h
+++ b/src/secp256k1/src/ecmult_const.h
@@ -1,3 +1,5 @@
+#ifndef ENABLE_MODULE_MUSIG
+
 /**********************************************************************
  * Copyright (c) 2015 Andrew Poelstra                                 *
  * Distributed under the MIT software license, see the accompanying   *
@@ -13,3 +15,24 @@
 static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, const secp256k1_scalar *q);
 
 #endif /* SECP256K1_ECMULT_CONST_H */
+
+#else
+/**********************************************************************
+ * Copyright (c) 2015 Andrew Poelstra                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef SECP256K1_ECMULT_CONST_H
+#define SECP256K1_ECMULT_CONST_H
+
+#include "scalar.h"
+#include "group.h"
+
+/* Here `bits` should be set to the maximum bitlength of the _absolute value_ of `q`, plus
+ * one because we internally sometimes add 2 to the number during the WNAF conversion. */
+static void secp256k1_ecmult_const(secp256k1_gej *r, const secp256k1_ge *a, const secp256k1_scalar *q, int bits);
+
+#endif /* SECP256K1_ECMULT_CONST_H */
+#endif
+