diff --git a/libcxx/include/string b/libcxx/include/string
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -618,18 +618,6 @@
 
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))
 
-#ifndef _LIBCPP_ABI_NO_BASIC_STRING_BASE_CLASS
-template <bool>
-struct __basic_string_common;
-
-template <>
-struct __basic_string_common<true> {
-    // Both are defined in string.cpp
-    _LIBCPP_NORETURN _LIBCPP_EXPORTED_FROM_ABI void __throw_length_error() const;
-    _LIBCPP_NORETURN _LIBCPP_EXPORTED_FROM_ABI void __throw_out_of_range() const;
-};
-#endif
-
 template <class _Iter>
 struct __string_is_trivial_iterator : public false_type {};
 
@@ -682,9 +670,6 @@
     _LIBCPP_PREFERRED_NAME(u32string)
 #endif
     basic_string
-#ifndef _LIBCPP_ABI_NO_BASIC_STRING_BASE_CLASS
-    : private __basic_string_common<true> // This base class is historical, but it needs to remain for ABI compatibility
-#endif
 {
 public:
     typedef basic_string                                 __self;
diff --git a/libcxx/src/string.cpp b/libcxx/src/string.cpp
--- a/libcxx/src/string.cpp
+++ b/libcxx/src/string.cpp
@@ -22,13 +22,21 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_ABI_NO_BASIC_STRING_BASE_CLASS
-void __basic_string_common<true>::__throw_length_error() const {
-    _VSTD::__throw_length_error("basic_string");
-}
 
-void __basic_string_common<true>::__throw_out_of_range() const {
-    _VSTD::__throw_out_of_range("basic_string");
-}
+template <bool>
+struct __basic_string_common;
+
+template <>
+struct __basic_string_common<true> {
+    // Both are defined in string.cpp
+    _LIBCPP_NORETURN _LIBCPP_EXPORTED_FROM_ABI void __throw_length_error() const {
+        _VSTD::__throw_length_error("basic_string");
+    }
+    _LIBCPP_NORETURN _LIBCPP_EXPORTED_FROM_ABI void __throw_out_of_range() const {
+        _VSTD::__throw_out_of_range("basic_string");
+    }
+};
+
 #endif
 
 #define _LIBCPP_EXTERN_TEMPLATE_DEFINE(...) template __VA_ARGS__;