Implement Vec<String>
diff --git a/src/cxx.cc b/src/cxx.cc
index b953904..e00fd6a 100644
--- a/src/cxx.cc
+++ b/src/cxx.cc
@@ -280,7 +280,8 @@
 
 #define FOR_EACH_RUST_VEC(MACRO)                                               \
   FOR_EACH_NUMERIC(MACRO)                                                      \
-  MACRO(bool, bool)
+  MACRO(bool, bool)                                                            \
+  MACRO(string, rust::String)
 
 extern "C" {
 FOR_EACH_STD_VECTOR(STD_VECTOR_OPS)