diff --git a/Modules/CMakeCXXCompiler.cmake.in b/Modules/CMakeCXXCompiler.cmake.in
index b264da1c9..e1b25d222 100644
--- a/Modules/CMakeCXXCompiler.cmake.in
+++ b/Modules/CMakeCXXCompiler.cmake.in
@@ -21,8 +21,8 @@ IF(CMAKE_COMPILER_IS_MINGW)
   SET(MINGW 1)
 ENDIF(CMAKE_COMPILER_IS_MINGW)
 SET(CMAKE_CXX_COMPILER_ID_RUN 1)
-SET(CMAKE_CXX_IGNORE_EXTENSIONS inl;h;H;o;O;obj;OBJ;def;DEF;rc;RC)
-SET(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;m;mm)
+SET(CMAKE_CXX_IGNORE_EXTENSIONS inl;h;hpp;HPP;H;o;O;obj;OBJ;def;DEF;rc;RC)
+SET(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;m;mm;C++;CC;CPP;CXX)
 SET(CMAKE_CXX_LINKER_PREFERENCE 30)
 SET(CMAKE_CXX_LINKER_PREFERENCE_PROPAGATES 1)
 
diff --git a/Tests/CxxOnly/CMakeLists.txt b/Tests/CxxOnly/CMakeLists.txt
index bfc827116..8418ad994 100644
--- a/Tests/CxxOnly/CMakeLists.txt
+++ b/Tests/CxxOnly/CMakeLists.txt
@@ -2,7 +2,7 @@
 project (CxxOnly CXX)
 
 set(CMAKE_DEBUG_POSTFIX "_test_debug_postfix")
-add_library(testcxx1 STATIC libcxx1.cxx)
+add_library(testcxx1 STATIC libcxx1.cxx test.CPP test.CXX test.C++)
 add_library(testcxx2 SHARED libcxx2.cxx)
 add_executable (CxxOnly cxxonly.cxx)
 target_link_libraries(CxxOnly testcxx1 testcxx2)
diff --git a/Tests/CxxOnly/cxxonly.cxx b/Tests/CxxOnly/cxxonly.cxx
index 99ccf3b61..2996e65c8 100644
--- a/Tests/CxxOnly/cxxonly.cxx
+++ b/Tests/CxxOnly/cxxonly.cxx
@@ -1,10 +1,14 @@
 #include "libcxx1.h"
 #include "libcxx2.h"
+extern int testCPP;
+extern int testCXX;
+extern int testCplusplus;
 
 #include <stdio.h>
 
 int main ()
 {
+  testCPP = testCXX= testCplusplus = 1;
   if ( LibCxx1Class::Method() != 2.0 )
     {
     printf("Problem with libcxx1\n");
diff --git a/Tests/CxxOnly/test.C++ b/Tests/CxxOnly/test.C++
new file mode 100644
index 000000000..6049ef12d
--- /dev/null
+++ b/Tests/CxxOnly/test.C++
@@ -0,0 +1 @@
+int testCplusplus;
diff --git a/Tests/CxxOnly/test.CPP b/Tests/CxxOnly/test.CPP
new file mode 100644
index 000000000..8a3cde262
--- /dev/null
+++ b/Tests/CxxOnly/test.CPP
@@ -0,0 +1 @@
+int testCPP;
diff --git a/Tests/CxxOnly/test.CXX b/Tests/CxxOnly/test.CXX
new file mode 100644
index 000000000..c05f7881a
--- /dev/null
+++ b/Tests/CxxOnly/test.CXX
@@ -0,0 +1 @@
+int testCXX;