diff --git a/src/at.c b/src/at.c
index ff77fbc..2527bca 100644
--- a/src/at.c
+++ b/src/at.c
@@ -58,15 +58,28 @@ gboolean at_send_command(struct EG25Manager *manager)
 
 	/* Send AT command */
         if (at_cmd->subcmd == NULL && at_cmd->value == NULL && at_cmd->expected == NULL)
-            len = sprintf(command, "AT+%s\r\n", at_cmd->cmd);
+            len = snprintf(command, sizeof(command), "AT+%s\r\n", at_cmd->cmd);
         else if (at_cmd->subcmd == NULL && at_cmd->value == NULL)
-            len = sprintf(command, "AT+%s?\r\n", at_cmd->cmd);
+            len = snprintf(command, sizeof(command), "AT+%s?\r\n", at_cmd->cmd);
         else if (at_cmd->subcmd == NULL && at_cmd->value)
-            len = sprintf(command, "AT+%s=%s\r\n", at_cmd->cmd, at_cmd->value);
+            len = snprintf(command,  sizeof(command),"AT+%s=%s\r\n", at_cmd->cmd, at_cmd->value);
         else if (at_cmd->subcmd && at_cmd->value == NULL)
-            len = sprintf(command, "AT+%s=\"%s\"\r\n", at_cmd->cmd, at_cmd->subcmd);
+            len = snprintf(command, sizeof(command), "AT+%s=\"%s\"\r\n", at_cmd->cmd, at_cmd->subcmd);
         else if (at_cmd->subcmd && at_cmd->value)
-            len = sprintf(command, "AT+%s=\"%s\",%s\r\n", at_cmd->cmd, at_cmd->subcmd, at_cmd->value);
+            len = snprintf(command, sizeof(command), "AT+%s=\"%s\",%s\r\n", at_cmd->cmd, at_cmd->subcmd, at_cmd->value);
+
+        if (len < 0) {
+            g_warning("snprintf(3) failed");
+            at_next_command(manager);
+            return FALSE;
+        }
+        else if (len >= sizeof(command)) {
+            g_warning("AT command does not fit into buffer "
+                "(%d bytes required, %zu available)", len, sizeof(command));
+            at_next_command(manager);
+            return FALSE;
+        }
+
         manager->at_callback = at_cmd->callback;
 
         ret = write(manager->at_fd, command, len);