diff --git a/compiler/cpp/src/thriftl.ll b/compiler/cpp/src/thriftl.ll
index 0889a12..21a0dd7 100644
--- a/compiler/cpp/src/thriftl.ll
+++ b/compiler/cpp/src/thriftl.ll
@@ -73,6 +73,7 @@
 "cpp_type"           { return tok_cpp_type;             }
 "java_package"       { return tok_java_package;         }
 "cocoa_prefix"       { return tok_cocoa_prefix;         }
+"csharp_namespace"   { return tok_csharp_namespace;     }
 "php_namespace"      { return tok_php_namespace;        }
 "py_module"          { return tok_py_module;            }
 "perl_package"       { return tok_perl_package;         }