diff --git a/Makefile b/Makefile
index e45899e91..58afaa237 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 # This file is released under the BSD license, see the COPYING file
 
 DEBUG?= -g
-CFLAGS?= -O2 -Wall -W -DSDS_ABORT_ON_OOM
+CFLAGS?= -std=c99 -pedantic -O2 -Wall -W -DSDS_ABORT_ON_OOM
 CCOPT= $(CFLAGS)
 
 OBJ = adlist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o
diff --git a/sds.h b/sds.h
index ba2a5ca0b..0fc2c9281 100644
--- a/sds.h
+++ b/sds.h
@@ -38,7 +38,7 @@ typedef char *sds;
 struct sdshdr {
     long len;
     long free;
-    char buf[0];
+    char buf[];
 };
 
 sds sdsnewlen(const void *init, size_t initlen);