diff --git a/SWIG/Lib/csharp/csharphead.swg b/SWIG/Lib/csharp/csharphead.swg
index 63461909c..cd78a963a 100644
--- a/SWIG/Lib/csharp/csharphead.swg
+++ b/SWIG/Lib/csharp/csharphead.swg
@@ -162,4 +162,8 @@ extern "C"
 DllExport void SWIGSTDCALL SWIGRegisterStringCallback_$module(SWIG_CSharpStringHelperCallback callback) {
   SWIG_csharp_string_callback = callback;
 }
+
+/* Contract support */
+
+#define SWIG_contract_assert(nullreturn, expr, msg) if (!(expr)) {SWIG_JavaThrowException(jenv, SWIG_JavaIllegalArgumentException, msg); return nullreturn; } else
 %}