diff --git a/include/__config b/include/__config
index e49adb4..a8991c3 100644
--- a/include/__config
+++ b/include/__config
@@ -1429,6 +1429,15 @@
 
 #define _LIBCPP_UNUSED_VAR(x) ((void)(x))
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+#define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName) \
+  template <class _Tag = void> \
+  _ClassName(typename _Tag::__allow_ctad) -> _ClassName<void>
+#else
+#define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName) \
+   static_assert(true, "")
+#endif // _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG
diff --git a/include/__mutex_base b/include/__mutex_base
index f828bea..6361c20 100644
--- a/include/__mutex_base
+++ b/include/__mutex_base
@@ -107,6 +107,8 @@
     lock_guard(lock_guard const&) _LIBCPP_EQUAL_DELETE;
     lock_guard& operator=(lock_guard const&) _LIBCPP_EQUAL_DELETE;
 };
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(lock_guard);
+
 
 template <class _Mutex>
 class _LIBCPP_TEMPLATE_VIS unique_lock
@@ -205,6 +207,7 @@
     _LIBCPP_INLINE_VISIBILITY
     mutex_type* mutex() const _NOEXCEPT {return __m_;}
 };
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(unique_lock);
 
 template <class _Mutex>
 void
diff --git a/include/functional b/include/functional
index 865a281..dd65f1b 100644
--- a/include/functional
+++ b/include/functional
@@ -3067,7 +3067,8 @@
     _ForwardIterator __first_;
     _ForwardIterator __last_;
     _BinaryPredicate __pred_;
-    };
+};
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(default_searcher);
 
 #endif // _LIBCPP_STD_VER > 14
 
diff --git a/include/iterator b/include/iterator
index 30801ea..b503f15 100644
--- a/include/iterator
+++ b/include/iterator
@@ -841,6 +841,7 @@
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator++()    {return *this;}
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator  operator++(int) {return *this;}
 };
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(back_insert_iterator);
 
 template <class _Container>
 inline _LIBCPP_INLINE_VISIBILITY
diff --git a/include/mutex b/include/mutex
index 20c3ffc..a7d6232 100644
--- a/include/mutex
+++ b/include/mutex
@@ -546,6 +546,7 @@
 
     _MutexTuple __t_;
 };
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(scoped_lock);
 
 #endif // _LIBCPP_STD_VER > 14
 #endif // !_LIBCPP_HAS_NO_THREADS
diff --git a/include/shared_mutex b/include/shared_mutex
index fcafd8c..c991134 100644
--- a/include/shared_mutex
+++ b/include/shared_mutex
@@ -430,6 +430,7 @@
     _LIBCPP_INLINE_VISIBILITY
     mutex_type* mutex() const _NOEXCEPT {return __m_;}
 };
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(shared_lock);
 
 template <class _Mutex>
 void
diff --git a/include/string_view b/include/string_view
index 0444831..39ebc66 100644
--- a/include/string_view
+++ b/include/string_view
@@ -604,6 +604,7 @@
     const   value_type* __data;
     size_type           __size;
 };
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(basic_string_view);
 
 
 // [string.view.comparison]
diff --git a/test/std/iterators/predef.iterators/insert.iterators/back.insert.iterator/implicit_ctad.pass.cpp b/test/std/iterators/predef.iterators/insert.iterators/back.insert.iterator/implicit_ctad.pass.cpp
new file mode 100644
index 0000000..7c4ba6a
--- /dev/null
+++ b/test/std/iterators/predef.iterators/insert.iterators/back.insert.iterator/implicit_ctad.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+// class back_insert_iterator.
+
+#include <string>
+#include <iterator>
+#include <vector>
+#include <cassert>
+#include <cstddef>
+#include <functional>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    {
+      std::string s;
+      std::back_insert_iterator bs(s);
+      ASSERT_SAME_TYPE(decltype(bs), std::back_insert_iterator<std::string>);
+    }
+  {
+    std::vector<int> v;
+    std::back_insert_iterator bv(v);
+    std::back_insert_iterator cp(bv);
+    ASSERT_SAME_TYPE(decltype(bv), std::back_insert_iterator<std::vector<int>>);
+    ASSERT_SAME_TYPE(decltype(cp), std::back_insert_iterator<std::vector<int>>);
+  }
+
+  return 0;
+}
diff --git a/utils/libcxx/test/config.py b/utils/libcxx/test/config.py
index 82951b7..6552d30 100644
--- a/utils/libcxx/test/config.py
+++ b/utils/libcxx/test/config.py
@@ -911,6 +911,7 @@
         self.cxx.addWarningFlagIfSupported('-Wunused-variable')
         self.cxx.addWarningFlagIfSupported('-Wunused-parameter')
         self.cxx.addWarningFlagIfSupported('-Wunreachable-code')
+        self.cxx.addWarningFlagIfSupported('-Wctad-maybe-unsupported')
         std = self.get_lit_conf('std', None)
         if std in ['c++98', 'c++03']:
             # The '#define static_assert' provided by libc++ in C++03 mode