diff --git a/client/hardnested/hardnested_tables.c b/client/hardnested/hardnested_tables.c
index 912ad5cc4..91e3b3cd3 100644
--- a/client/hardnested/hardnested_tables.c
+++ b/client/hardnested/hardnested_tables.c
@@ -20,7 +20,7 @@
 //-----------------------------------------------------------------------------
 
 // To compile it:
-// gcc -I ../../common -o hardnested_tables hardnested_tables.c
+// gcc -std=c99 -I ../../common -o hardnested_tables hardnested_tables.c
 
 #include <inttypes.h>
 #include <stdbool.h>