@@ -516,11 +516,11 @@
 	AC_MSG_ERROR(No asprintf and no snprintf returning required space!)
 
 AC_CHECK_FUNCS([arc4random random], break)
 
 AC_CHECK_LIB(dl, dlopen, LIBS="$LIBS -ldl")
-AC_CHECK_HEADERS(dlfcn.h)
+AC_CHECK_HEADERS_ONCE(dlfcn.h)
 case "$host_os" in
 	netbsd*)
 		dnl dladdr exists on NetBSD, but it is completely broken.
 		dnl When using it with code that uses __thread, it freezes the
 		dnl process so that it has to be killed using SIGKILL.
@@ -593,11 +593,11 @@
 
 	AC_ARG_ENABLE(compiler-tls,
 		AS_HELP_STRING([--disable-compiler-tls],
 			[disable compiler thread local storage]))
 	AS_IF([test x"$enable_compiler_tls" != x"no"], [
-		AC_CHECK_HEADERS(threads.h, [
+		AC_CHECK_HEADER(threads.h, [
 			AC_DEFINE(OF_HAVE_THREADS_H, 1,
 				[Whether we have threads.h])
 		])
 
 		AC_MSG_CHECKING(whether _Thread_local works)
@@ -765,15 +765,15 @@
 
 	AC_CHECK_HEADER(sys/socket.h, [
 		AC_DEFINE(OF_HAVE_SYS_SOCKET_H, 1,
 			[Whether we have sys/socket.h])
 	])
-	AC_CHECK_HEADERS(netinet/in.h, [
+	AC_CHECK_HEADER(netinet/in.h, [
 		AC_DEFINE(OF_HAVE_NETINET_IN_H, 1,
 			[Whether we have netinet/in.h])
 	])
-	AC_CHECK_HEADERS(netinet/tcp.h, [
+	AC_CHECK_HEADER(netinet/tcp.h, [
 		AC_DEFINE(OF_HAVE_NETINET_TCP_H, 1,
 			[Whether we have netinet/tcp.h])
 	])
 	AC_CHECK_HEADERS([arpa/inet.h netdb.h])
 
@@ -962,11 +962,11 @@
 AS_IF([test x"$have_processes" = x"yes"], [
 	AC_SUBST(OFPROCESS_M, "OFProcess.m")
 	AC_DEFINE(OF_HAVE_PROCESSES, 1, [Whether we have processes])
 ])
 
-AC_CHECK_HEADERS([sys/ioctl.h sys/termios.h])
+AC_CHECK_HEADERS_ONCE([sys/ioctl.h sys/termios.h])
 
 AS_IF([test x"$objc_runtime" = x"Apple runtime"], [
 	AC_CHECK_HEADER(Foundation/NSObject.h, [
 		AC_SUBST(FOUNDATION_COMPAT_M, "foundation-compat.m")
 		AC_SUBST(BRIDGE, "bridge")