diff --git a/configure.ac b/configure.ac
index 78d6e8ac..83d28b85 100644
--- a/configure.ac
+++ b/configure.ac
@@ -834,15 +834,14 @@ AC_C_BIGENDIAN
 # Use -Werror because some compilers accept unknown attributes and just
 # give a warning. If it works this should give no warnings, even
 # clang -Weverything should be fine.
-# dnl This doesn't need AC_LANG_SOURCE, minimal code is enough.
 AC_MSG_CHECKING([if __attribute__((__constructor__)) can be used])
 have_func_attribute_constructor=no
 OLD_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -Werror"
-AC_COMPILE_IFELSE([
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 	__attribute__((__constructor__))
 	static void my_constructor_func(void) { return; }
-], [
+]])], [
 	AC_DEFINE([HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR], [1],
 		[Define to 1 if __attribute__((__constructor__))
 		is supported for functions.])
@@ -878,12 +877,12 @@ if test "x$enable_ifunc" = xyes ; then
 	OLD_CFLAGS="$CFLAGS"
 	CFLAGS="$CFLAGS -Werror"
 	AC_MSG_CHECKING([if __attribute__((__ifunc__())) can be used])
-	AC_COMPILE_IFELSE([
+	AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 		static void func(void) { return; }
 		static void (*resolve_func (void)) (void) { return func; }
 		void func_ifunc (void)
 				__attribute__((__ifunc__("resolve_func")));
-	], [
+	]])], [
 		AC_DEFINE([HAVE_FUNC_ATTRIBUTE_IFUNC], [1],
 			[Define to 1 if __attribute__((__ifunc__()))
 			is supported for functions.])