diff --git a/libcxx/test/libcxx/clang_tidy.sh.cpp b/libcxx/test/libcxx/clang_tidy.sh.cpp
--- a/libcxx/test/libcxx/clang_tidy.sh.cpp
+++ b/libcxx/test/libcxx/clang_tidy.sh.cpp
@@ -229,12 +229,6 @@
 #    include <experimental/vector>
 #endif // __cplusplus >= 201103L
 
-// extended headers
-#ifndef _LIBCXX_MODULES_BUILD
-#    include <ext/hash_map>
-#    include <ext/hash_set>
-#endif
-
 // clang-format on
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/test/libcxx/double_include.sh.cpp b/libcxx/test/libcxx/double_include.sh.cpp
--- a/libcxx/test/libcxx/double_include.sh.cpp
+++ b/libcxx/test/libcxx/double_include.sh.cpp
@@ -230,12 +230,6 @@
 #    include <experimental/vector>
 #endif // __cplusplus >= 201103L
 
-// extended headers
-#ifndef _LIBCXX_MODULES_BUILD
-#    include <ext/hash_map>
-#    include <ext/hash_set>
-#endif
-
 // clang-format on
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/test/libcxx/min_max_macros.compile.pass.cpp b/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
--- a/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
+++ b/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
@@ -365,14 +365,6 @@
 TEST_MACROS();
 #endif // __cplusplus >= 201103L
 
-// extended headers
-#ifndef _LIBCXX_MODULES_BUILD
-#    include <ext/hash_map>
-TEST_MACROS();
-#    include <ext/hash_set>
-TEST_MACROS();
-#endif
-
 // clang-format on
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/test/libcxx/nasty_macros.compile.pass.cpp b/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
--- a/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
+++ b/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
@@ -340,12 +340,6 @@
 #    include <experimental/vector>
 #endif // __cplusplus >= 201103L
 
-// extended headers
-#ifndef _LIBCXX_MODULES_BUILD
-#    include <ext/hash_map>
-#    include <ext/hash_set>
-#endif
-
 // clang-format on
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/test/libcxx/no_assert_include.compile.pass.cpp b/libcxx/test/libcxx/no_assert_include.compile.pass.cpp
--- a/libcxx/test/libcxx/no_assert_include.compile.pass.cpp
+++ b/libcxx/test/libcxx/no_assert_include.compile.pass.cpp
@@ -225,12 +225,6 @@
 #    include <experimental/vector>
 #endif // __cplusplus >= 201103L
 
-// extended headers
-#ifndef _LIBCXX_MODULES_BUILD
-#    include <ext/hash_map>
-#    include <ext/hash_set>
-#endif
-
 // clang-format on
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/utils/generate_header_tests.py b/libcxx/utils/generate_header_tests.py
--- a/libcxx/utils/generate_header_tests.py
+++ b/libcxx/utils/generate_header_tests.py
@@ -91,11 +91,6 @@
 #if __cplusplus >= 201103L
 {experimental_headers}
 #endif // __cplusplus >= 201103L
-
-// extended headers
-#ifndef _LIBCXX_MODULES_BUILD
-{extended_headers}
-#endif
 """
 
 
@@ -193,9 +188,6 @@
         experimental_headers=produce_experimental_headers(
             post_include=post_include,
         ),
-        extended_headers=produce_extended_headers(
-            post_include=post_include,
-        ),
     )
 
     replace_generated_headers(os.path.join(
diff --git a/libcxx/utils/libcxx/test/params.py b/libcxx/utils/libcxx/test/params.py
--- a/libcxx/utils/libcxx/test/params.py
+++ b/libcxx/utils/libcxx/test/params.py
@@ -77,7 +77,6 @@
               AddFeature('modules-build'),
               AddCompileFlag('-fmodules'),
               AddCompileFlag('-fcxx-modules'), # AppleClang disregards -fmodules entirely when compiling C++. This enables modules for C++.
-              AddCompileFlag('-D_LIBCXX_MODULES_BUILD') # Needed to exclude headers that are not supported in a modules build
             ] if modules else []),
 
   Parameter(name='enable_exceptions', choices=[True, False], type=bool, default=True,