diff --git a/cmake/ConfigureChecks.cmake b/cmake/ConfigureChecks.cmake
index 863213f81..1ba570f5e 100644
--- a/cmake/ConfigureChecks.cmake
+++ b/cmake/ConfigureChecks.cmake
@@ -358,7 +358,9 @@ if(HAVE_BUILTIN_OPENPTY)
   set(HAVE_LIBUTIL 1)
 else()
   find_library(HAVE_LIBUTIL util)
-  set(LIBUTIL_LIBRARIES ${HAVE_LIBUTIL})
+  if(HAVE_LIBUTIL)
+    set(LIBUTIL_LIBRARIES ${HAVE_LIBUTIL})
+  endif()
 endif()
 
 if(APPLE)
@@ -540,6 +542,18 @@ elseif(CMAKE_SYSTEM MATCHES "QNX\\-6\\.3\\.2$")
   # defining NI_NUMERICHOST.
 
   set(define_xopen_source 0)
+
+elseif(CMAKE_SYSTEM MATCHES "VxWorks\\-7$")
+
+  # VxWorks-7
+
+  # On VxWorks-7, defining _XOPEN_SOURCE or _POSIX_C_SOURCE 
+  # leads to a failure in select.h because sys/types.h fails
+  # to define FD_SETSIZE.
+  # Reported by Martin Oberhuber as V7COR-4651.
+
+  set(define_xopen_source 0)
+
 endif()
 
 if(define_xopen_source)
diff --git a/cmake/extensions/CMakeLists.txt b/cmake/extensions/CMakeLists.txt
index 9aea823e9..5899f6deb 100644
--- a/cmake/extensions/CMakeLists.txt
+++ b/cmake/extensions/CMakeLists.txt
@@ -1,17 +1,18 @@
-# XXX Because of CMake issue #8170 disable ctypes support when using
-#     "Visual Studio 2008 Win64" generator.
-if("${MSVC_VERSION}" VERSION_EQUAL 1500 AND ${CMAKE_SIZEOF_VOID_P} EQUAL 8)
+if(MSVC_VERSION)
+  # XXX Because of CMake issue #8170 disable ctypes support when using
+  #     "Visual Studio 2008 Win64" generator.
+  if("${MSVC_VERSION}" VERSION_EQUAL 1500 AND ${CMAKE_SIZEOF_VOID_P} EQUAL 8)
     set(warn "Disable 'ctypes' and 'ctypes_test' extensions when using 'Visual Studio 2008 Win64' generator. See http://public.kitware.com/Bug/view.php?id=8170 for more details.")
     if(NOT DEFINED ENABLE_CTYPES OR ENABLE_CTYPES OR NOT DEFINED ENABLE_CTYPES_TEST OR ENABLE_CTYPES_TEST)
         message(WARNING ${warn})
     endif()
     set(ENABLE_CTYPES OFF CACHE BOOL "${warn}" FORCE)
     set(ENABLE_CTYPES_TEST OFF CACHE BOOL "${warn}" FORCE)
-endif()
-# XXX Because of CMake issue #11536, disable ctypes support when using
-#     CMake < 2.8.12 with "Visual Studio 2010" and "Visual Studio 2010 Win64"
-#     generator.
-if(CMAKE_VERSION VERSION_LESS 2.8.12)
+  endif()
+  # XXX Because of CMake issue #11536, disable ctypes support when using
+  #     CMake < 2.8.12 with "Visual Studio 2010" and "Visual Studio 2010 Win64"
+  #     generator.
+  if(CMAKE_VERSION VERSION_LESS 2.8.12)
     if("${MSVC_VERSION}" VERSION_EQUAL 1600)
         set(warn "Disable 'ctypes' and 'ctypes_test' extensions when using CMake < 2.8.12 with any 'Visual Studio 2010' generators. See http://public.kitware.com/Bug/view.php?id=11536 for more details.")
         if(NOT DEFINED ENABLE_CTYPES OR ENABLE_CTYPES OR NOT DEFINED ENABLE_CTYPES_TEST OR ENABLE_CTYPES_TEST)
@@ -20,6 +21,7 @@ if(CMAKE_VERSION VERSION_LESS 2.8.12)
         set(ENABLE_CTYPES OFF CACHE BOOL "${warn}" FORCE)
         set(ENABLE_CTYPES_TEST OFF CACHE BOOL "${warn}" FORCE)
     endif()
+  endif()
 endif()
 
 set(WIN32_BUILTIN )