diff --git a/README.md b/README.md
index f65ff7b..14d4269 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ Each of the flags has a corresponding environment variable:
 
 -   `Q3RCON_PROXY_HOST`: The host the proxy server sits on.
 -   `Q3RCON_TARGET_HOST`: The host the game servers sit on.
--   `Q3RCON_PORTS_MAPPING`: A mapping as a with `source:target` pairs delimited by `;`.
+-   `Q3RCON_PORTS_MAPPING`: A mapping as a string with `source:target` pairs delimited by `;`.
 -   `Q3RCON_SESSION_TIMEOUT`: Timeout in seconds for each udp session.
 -   `Q3RCON_LOGLEVEL`: The application's logging level (see [Logging][logging]).