diff --git a/Modules/CMakeCXXCompiler.cmake.in b/Modules/CMakeCXXCompiler.cmake.in
index ef65021..efb8abf 100644
--- a/Modules/CMakeCXXCompiler.cmake.in
+++ b/Modules/CMakeCXXCompiler.cmake.in
@@ -45,7 +45,7 @@
 set(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;m;mm;CPP)
 set(CMAKE_CXX_IGNORE_EXTENSIONS inl;h;hpp;HPP;H;o;O;obj;OBJ;def;DEF;rc;RC)
 
-foreach (lang OBJC OBJCXX)
+foreach (lang C OBJC OBJCXX)
   if (CMAKE_${lang}_COMPILER_ID_RUN)
     foreach(extension IN LISTS CMAKE_${lang}_SOURCE_FILE_EXTENSIONS)
       list(REMOVE_ITEM CMAKE_CXX_SOURCE_FILE_EXTENSIONS ${extension})
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index 32b580b..b29638b 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -2353,6 +2353,18 @@
       )
       list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/Objective-C/c-file-extension-test")
 
+      add_test(Objective-C.cxx-file-extension-test ${CMAKE_CTEST_COMMAND}
+        --build-and-test
+        "${CMake_SOURCE_DIR}/Tests/Objective-C/cxx-file-extension-test"
+        "${CMake_BINARY_DIR}/Tests/Objective-C/cxx-file-extension-test"
+        --build-two-config
+        ${build_generator_args}
+        --build-project cxx-file-extension-test
+        --build-options ${build_options}
+        --test-command cxx-file-extension-test
+      )
+      list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/Objective-C/cxx-file-extension-test")
+
       add_test(Objective-C.objc-file-extension-test ${CMAKE_CTEST_COMMAND}
         --build-and-test
         "${CMake_SOURCE_DIR}/Tests/Objective-C/objc-file-extension-test"
diff --git a/Tests/Objective-C/cxx-file-extension-test/CMakeLists.txt b/Tests/Objective-C/cxx-file-extension-test/CMakeLists.txt
new file mode 100644
index 0000000..eb065e4
--- /dev/null
+++ b/Tests/Objective-C/cxx-file-extension-test/CMakeLists.txt
@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.15)
+
+project(cxx-file-extension-test)
+
+string(APPEND CMAKE_CXX_FLAGS " -std=c++11")
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(cxx-file-extension-test main.m)
diff --git a/Tests/Objective-C/cxx-file-extension-test/main.m b/Tests/Objective-C/cxx-file-extension-test/main.m
new file mode 100644
index 0000000..1c159a9
--- /dev/null
+++ b/Tests/Objective-C/cxx-file-extension-test/main.m
@@ -0,0 +1,8 @@
+#ifndef __OBJC__
+#  error "Compiler cannot compile Objective-C"
+#endif
+
+int main()
+{
+  return 0;
+}