diff --git a/openssl-net-0.5/ManagedOpenSsl/Core/BigNumber.cs b/openssl-net-0.5/ManagedOpenSsl/Core/BigNumber.cs
index a58076e..53c3ce2 100644
--- a/openssl-net-0.5/ManagedOpenSsl/Core/BigNumber.cs
+++ b/openssl-net-0.5/ManagedOpenSsl/Core/BigNumber.cs
@@ -268,7 +268,7 @@ public static BigNumber mod_inverse(BigNumber lhs, BigNumber rhs)
 			BigNumber ret = new BigNumber();
 			Context ctx = new Context();
 			ctx.Start();
-			Native.ExpectSuccess(Native.BN_mod_inverse(ret.Handle, lhs.Handle, rhs.Handle, ctx.Handle));
+			Native.ExpectNonNull(Native.BN_mod_inverse(ret.Handle, lhs.Handle, rhs.Handle, ctx.Handle));
 			ctx.End();
 			return ret;
 		}
@@ -495,4 +495,4 @@ protected override void OnDispose() {
 		}
 		#endregion
 	}
-}
\ No newline at end of file
+}
diff --git a/openssl-net-0.5/ManagedOpenSsl/Core/Native.cs b/openssl-net-0.5/ManagedOpenSsl/Core/Native.cs
index d4b5f0c..86692c1 100644
--- a/openssl-net-0.5/ManagedOpenSsl/Core/Native.cs
+++ b/openssl-net-0.5/ManagedOpenSsl/Core/Native.cs
@@ -1104,7 +1104,7 @@ int DSA_generate_parameters_ex(IntPtr dsa,
 		//[DllImport(DLLNAME, CallingConvention=CallingConvention.Cdecl)]
 		//public extern static int BN_div(IntPtr rv, IntPtr rem, IntPtr m, IntPtr d, IntPtr ctx);
 		[DllImport(DLLNAME, CallingConvention=CallingConvention.Cdecl)]
-		public extern static int BN_mod_inverse(IntPtr ret, IntPtr a, IntPtr c, IntPtr ctx);
+		public extern static IntPtr BN_mod_inverse(IntPtr ret, IntPtr a, IntPtr c, IntPtr ctx);
 		[DllImport(DLLNAME, CallingConvention=CallingConvention.Cdecl)]
 		public extern static int BN_gcd(IntPtr r, IntPtr a, IntPtr b, IntPtr ctx);