diff --git a/SWIG/Source/Modules/csharp.cxx b/SWIG/Source/Modules/csharp.cxx
index de488c89e..4a7f84e84 100644
--- a/SWIG/Source/Modules/csharp.cxx
+++ b/SWIG/Source/Modules/csharp.cxx
@@ -696,6 +696,9 @@ class CSHARP : public Language {
     /* Substitute the cleanup code */
     Replaceall(f->code,"$cleanup",cleanup);
 
+    /* Contract macro modification */
+    Replaceall(f->code, "SWIG_contract_assert(", "SWIG_contract_assert($null, ");
+
     if(!is_void_return)
       Replaceall(f->code,"$null","0");
     else
diff --git a/SWIG/Source/Modules/java.cxx b/SWIG/Source/Modules/java.cxx
index db6425b77..8ec952ee6 100644
--- a/SWIG/Source/Modules/java.cxx
+++ b/SWIG/Source/Modules/java.cxx
@@ -974,6 +974,9 @@ class JAVA : public Language {
     /* Substitute the cleanup code */
     Replaceall(f->code,"$cleanup",cleanup);
 
+    /* Contract macro modification */
+    Replaceall(f->code, "SWIG_contract_assert(", "SWIG_contract_assert($null, ");
+
     if(!is_void_return)
       Replaceall(f->code,"$null","0");
     else