Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -3,15 +3,17 @@
 
 AC_CANONICAL_HOST
 
 AC_LANG([Objective C])
 AC_PROG_OBJC
-AC_PROG_CPP
+AC_PROG_OBJCPP
 AC_PROG_LN_S
 AC_PROG_INSTALL
 AC_PROG_EGREP
 
+CPP="$OBJCPP"
+CPPFLAGS="$CPPFLAGS $OBJCPPFLAGS"
 OBJCFLAGS="$OBJCFLAGS -Wall -fobjc-exceptions"
 OBJCFLAGS="$OBJCFLAGS -fconstant-string-class=OFConstString"
 LIBS="$LIBS -lobjc"
 
 AX_CHECK_COMPILER_FLAGS(-pipe, [OBJCFLAGS="$OBJCFLAGS -pipe"])
@@ -195,10 +197,15 @@
 else
 	AC_SUBST(TESTS, "tests")
 fi
 
 BUILDSYS_TOUCH_DEPS
+
+dnl We don't call AC_PROG_CPP, but only AC_PROG_OBJCPP and set CPP to OBJCPP
+dnl and add OBJCPPFLAGS to CPPFLAGS, thus we need to AC_SUBST these ourself
+AC_SUBST(CPP)
+AC_SUBST(CPPFLAGS)
 
 AC_SUBST(PACKAGE, ObjFW)
 AC_CONFIG_FILES([buildsys.mk extra.mk objfw-config])
 AC_CONFIG_HEADERS(config.h)
 AC_OUTPUT

Index: m4/acx_pthread.m4
==================================================================
--- m4/acx_pthread.m4
+++ m4/acx_pthread.m4
@@ -80,11 +80,11 @@
 #   special exception to the GPL to apply to your modified version as well.
 
 AC_DEFUN([ACX_PTHREAD], [
 AC_REQUIRE([AC_CANONICAL_HOST])
 AC_LANG_SAVE
-AC_LANG_C
+AC_LANG_OBJC
 acx_pthread_ok=no
 
 # We used to check for pthread.h first, but this fails if pthread.h
 # requires special compiler flags (e.g. on True64 or Sequent).
 # It gets checked for in the link test anyway.