diff --git a/CMakeLists.txt b/CMakeLists.txt
index c0bde098..8f5047c6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -228,6 +228,10 @@ else()
     list(APPEND LIBCXX_CXX_FEATURE_FLAGS -DNDEBUG)
   endif()
 endif()
+# Static library
+if (NOT LIBCXX_ENABLE_SHARED)
+  list(APPEND LIBCXX_CXX_FEATURE_FLAGS -D_LIBCPP_BUILD_STATIC)
+endif()
 
 # This is the _ONLY_ place where add_definitions is called.
 add_definitions(
diff --git a/include/memory b/include/memory
index f80d699f..4e1f7046 100644
--- a/include/memory
+++ b/include/memory
@@ -3629,10 +3629,13 @@ public:
     long use_count() const _NOEXCEPT {return __shared_count::use_count();}
     __shared_weak_count* lock() _NOEXCEPT;
 
-    // purposefully not protected with #ifndef _LIBCPP_NO_RTTI because doing so
-    //  breaks ABI for those clients who need to compile their projects with
-    //    -fno-rtti and yet link against a libc++.dylib compiled without -fno-rtti.
+    // Define the function out only if we build static libc++ without RTTI.
+    // Otherwise we may break clients who need to compile their projects with
+    // -fno-rtti and yet link against a libc++.dylib compiled
+    // without -fno-rtti.
+#if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
     virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
+#endif
 private:
     virtual void __on_zero_shared_weak() _NOEXCEPT = 0;
 };