Index: tools/Makefile.am
===================================================================
--- tools/Makefile.am	(revision d21d01e585638b66be768d67bb4e325d50f88ebd)
+++ tools/Makefile.am	(revision 5e49e477912c55f01edbd8c838b63e99a80722bd)
@@ -18,5 +18,5 @@
 
 CC = @BACKEND_CC@
-AM_CFLAGS = -Wall -Wextra -O2 -g
+AM_CFLAGS = -Wall -Wextra -O2 -g -std=c11
 
 noinst_PROGRAMS = busy catchsig repeat watchdog
Index: tools/Makefile.in
===================================================================
--- tools/Makefile.in	(revision d21d01e585638b66be768d67bb4e325d50f88ebd)
+++ tools/Makefile.in	(revision 5e49e477912c55f01edbd8c838b63e99a80722bd)
@@ -305,5 +305,5 @@
 top_srcdir = @top_srcdir@
 AUTOMAKE_OPTIONS = foreign    # do not require all the GNU file names
-AM_CFLAGS = -Wall -Wextra -O2 -g
+AM_CFLAGS = -Wall -Wextra -O2 -g -std=c11
 busy_SOURCES = busy.c
 busy_LDFLAGS = -pthread