diff --git a/library/bignum.c b/library/bignum.c
index de61952..19d59be 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1547,7 +1547,7 @@
 
 static void mpi_montg_init( mbedtls_mpi_uint *mm, const mbedtls_mpi *N )
 {
-    *mm = mbedtls_mpi_montg_init( N->p );
+    *mm = mbedtls_mpi_core_montmul_init( N->p );
 }
 
 /** Montgomery multiplication: A = A * B * R^-1 mod N  (HAC 14.36)