diff --git a/ChangeLog b/ChangeLog
index 1df46aec..1220dc94 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,7 +3,9 @@
 	* acspecific.m4 (AC_EMXOS2): New macro. Contributed by Ryuji Abe
 	<raeva@t3.rim.or.jp>.
 	(AC_EXEEXT): Handle case for OS/2.
-	
+	(AC_PROG_CC_WORKS): Show $CPPFLAGS when running the compiler.
+	(AC_PROG_CXX_WORKS): Likewise.
+
 	* autoconf.texi (AC_EMXOS2): Document.
 	(AC_EXEEXT): Mention OS/2.
 	(AC_MINGW32): Move.
diff --git a/acspecific.m4 b/acspecific.m4
index 2890660f..bac0955e 100644
--- a/acspecific.m4
+++ b/acspecific.m4
@@ -199,7 +199,7 @@ fi
 ])
 
 AC_DEFUN(AC_PROG_CC_WORKS,
-[AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $LDFLAGS) works])
+[AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $CPPFLAGS $LDFLAGS) works])
 AC_LANG_SAVE
 AC_LANG_C
 AC_TRY_COMPILER([main(){return(0);}], ac_cv_prog_cc_works, ac_cv_prog_cc_cross)
@@ -208,13 +208,13 @@ AC_MSG_RESULT($ac_cv_prog_cc_works)
 if test $ac_cv_prog_cc_works = no; then
   AC_MSG_ERROR([installation or configuration problem: C compiler cannot create executables.])
 fi
-AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $LDFLAGS) is a cross-compiler])
+AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $CPPFLAGS $LDFLAGS) is a cross-compiler])
 AC_MSG_RESULT($ac_cv_prog_cc_cross)
 cross_compiling=$ac_cv_prog_cc_cross
 ])
 
 AC_DEFUN(AC_PROG_CXX_WORKS,
-[AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $LDFLAGS) works])
+[AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $CPPFLAGS $LDFLAGS) works])
 AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILER([int main(){return(0);}], ac_cv_prog_cxx_works, ac_cv_prog_cxx_cross)
@@ -223,7 +223,7 @@ AC_MSG_RESULT($ac_cv_prog_cxx_works)
 if test $ac_cv_prog_cxx_works = no; then
   AC_MSG_ERROR([installation or configuration problem: C++ compiler cannot create executables.])
 fi
-AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $LDFLAGS) is a cross-compiler])
+AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $CPPFLAGS $LDFLAGS) is a cross-compiler])
 AC_MSG_RESULT($ac_cv_prog_cxx_cross)
 cross_compiling=$ac_cv_prog_cxx_cross
 ])
diff --git a/lib/autoconf/specific.m4 b/lib/autoconf/specific.m4
index 2890660f..bac0955e 100644
--- a/lib/autoconf/specific.m4
+++ b/lib/autoconf/specific.m4
@@ -199,7 +199,7 @@ fi
 ])
 
 AC_DEFUN(AC_PROG_CC_WORKS,
-[AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $LDFLAGS) works])
+[AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $CPPFLAGS $LDFLAGS) works])
 AC_LANG_SAVE
 AC_LANG_C
 AC_TRY_COMPILER([main(){return(0);}], ac_cv_prog_cc_works, ac_cv_prog_cc_cross)
@@ -208,13 +208,13 @@ AC_MSG_RESULT($ac_cv_prog_cc_works)
 if test $ac_cv_prog_cc_works = no; then
   AC_MSG_ERROR([installation or configuration problem: C compiler cannot create executables.])
 fi
-AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $LDFLAGS) is a cross-compiler])
+AC_MSG_CHECKING([whether the C compiler ($CC $CFLAGS $CPPFLAGS $LDFLAGS) is a cross-compiler])
 AC_MSG_RESULT($ac_cv_prog_cc_cross)
 cross_compiling=$ac_cv_prog_cc_cross
 ])
 
 AC_DEFUN(AC_PROG_CXX_WORKS,
-[AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $LDFLAGS) works])
+[AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $CPPFLAGS $LDFLAGS) works])
 AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILER([int main(){return(0);}], ac_cv_prog_cxx_works, ac_cv_prog_cxx_cross)
@@ -223,7 +223,7 @@ AC_MSG_RESULT($ac_cv_prog_cxx_works)
 if test $ac_cv_prog_cxx_works = no; then
   AC_MSG_ERROR([installation or configuration problem: C++ compiler cannot create executables.])
 fi
-AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $LDFLAGS) is a cross-compiler])
+AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $CPPFLAGS $LDFLAGS) is a cross-compiler])
 AC_MSG_RESULT($ac_cv_prog_cxx_cross)
 cross_compiling=$ac_cv_prog_cxx_cross
 ])