diff --git a/apps/shell/shell-vars.c b/apps/shell/shell-vars.c
index 1e562d944..84b7724e9 100644
--- a/apps/shell/shell-vars.c
+++ b/apps/shell/shell-vars.c
@@ -91,7 +91,7 @@ PROCESS_THREAD(shell_var_process, ev, data)
   int i;
   int j;
   
-  char numbuf[39];
+  char numbuf[40];
   
   PROCESS_BEGIN();