diff --git a/src/include/refstring.h b/src/include/refstring.h
index 0675b39..c32630c 100644
--- a/src/include/refstring.h
+++ b/src/include/refstring.h
@@ -13,7 +13,13 @@
 #include <stdexcept>
 #include <cstddef>
 #include <cstring>
+
+#if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_CXX03_LANG) && !defined(_LIBCPP_USE_ATOMIC)
+#define _LIBCPP_USE_ATOMIC
+#include <atomic>
+#else
 #include "atomic_support.h"
+#endif
 
 // MacOS and iOS used to ship with libstdc++, and still support old applications
 // linking against libstdc++. The libc++ and libstdc++ exceptions are supposed
@@ -40,7 +46,11 @@ typedef int count_t;
 struct _Rep_base {
     std::size_t len;
     std::size_t cap;
+#ifdef _LIBCPP_USE_ATOMIC
+    std::atomic<count_t> count;
+#else
     count_t     count;
+#endif
 };
 
 inline _Rep_base* rep_from_data(const char *data_) noexcept {
@@ -96,7 +106,11 @@ __libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) noexcept
     : __imp_(s.__imp_)
 {
     if (__uses_refcount())
+#ifdef _LIBCPP_USE_ATOMIC
+        rep_from_data(__imp_)->count.fetch_add(1);
+#else
         __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
+#endif
 }
 
 inline
@@ -105,10 +119,19 @@ __libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) n
     struct _Rep_base *old_rep = rep_from_data(__imp_);
     __imp_ = s.__imp_;
     if (__uses_refcount())
+#ifdef _LIBCPP_USE_ATOMIC
+        rep_from_data(__imp_)->count.fetch_add(1);
+#else
         __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
+#endif
+
     if (adjust_old_count)
     {
+#ifdef _LIBCPP_USE_ATOMIC
+        if (old_rep->count.fetch_sub(1) == 0)
+#else
         if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0)
+#endif
         {
             ::operator delete(old_rep);
         }
@@ -120,7 +143,11 @@ inline
 __libcpp_refstring::~__libcpp_refstring() {
     if (__uses_refcount()) {
         _Rep_base* rep = rep_from_data(__imp_);
+#ifdef _LIBCPP_USE_ATOMIC
+        if (rep->count.fetch_sub(1) == 0) {
+#else
         if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) {
+#endif
             ::operator delete(rep);
         }
     }