diff --git a/ffi/cs/mcl/mcl.cs b/ffi/cs/mcl/mcl.cs
index 133186d..24fc55d 100644
--- a/ffi/cs/mcl/mcl.cs
+++ b/ffi/cs/mcl/mcl.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Text;
 using System.Runtime.InteropServices;
 
@@ -73,7 +73,7 @@ namespace mcl {
         [DllImport(dllName)] public static extern void mclBnG1_add(ref G1 z, in G1 x, in G1 y);
         [DllImport(dllName)] public static extern void mclBnG1_sub(ref G1 z, in G1 x, in G1 y);
         [DllImport(dllName)] public static extern void mclBnG1_mul(ref G1 z, in G1 x, in Fr y);
-        [DllImport(dllName)] public static extern void mclBnG1_mulVec(ref G1 x, [In]G1[] vec1, [In]Fr[] vec2, long bufSize);
+        [DllImport(dllName)] public static extern void mclBnG1_mulVec(ref G1 z, [In]G1[] x, [In]Fr[] y, long n);
 
         [DllImport(dllName)] public static extern void mclBnG2_clear(ref G2 x);
         [DllImport(dllName)] public static extern int mclBnG2_setStr(ref G2 x, [In][MarshalAs(UnmanagedType.LPStr)] string buf, long bufSize, int ioMode);
@@ -217,6 +217,14 @@ namespace mcl {
         {
             mclBnG1_normalize(ref y, x);
         }
+        public static void MulVec(ref G1 z, in G1[] x, in Fr[] y)
+        {
+            int n = x.Length;
+            if (n <= 0 || n != y.Length) {
+                throw new ArgumentException("bad length");
+            }
+            mclBnG1_mulVec(ref z, x, y, (long)n);
+        }
         public static void Add(ref G2 z, in G2 x, in G2 y)
         {
             mclBnG2_add(ref z, x, y);
diff --git a/ffi/cs/test/test.cs b/ffi/cs/test/test.cs
index c9393e3..2972cc8 100644
--- a/ffi/cs/test/test.cs
+++ b/ffi/cs/test/test.cs
@@ -164,6 +164,20 @@ namespace mcl {
                 Q.Deserialize(buf);
                 assert("P == Q", P.Equals(Q));
             }
+            {
+                const int n = 5;
+                G1[] xVec = new G1[n];
+                Fr[] yVec = new Fr[n];
+                P.Clear();
+                for (int i = 0; i < n; i++) {
+                    xVec[i].HashAndMapTo(i.ToString());
+                    yVec[i].SetByCSPRNG();
+                    Q.Mul(xVec[i], yVec[i]);
+                    P.Add(P, Q);
+                }
+                MulVec(ref Q, xVec, yVec);
+                assert("mulVecG1", P.Equals(Q));
+            }
         }
         static void TestG2()
         {