diff --git a/pkgs/servers/mail/postfix/default.nix b/pkgs/servers/mail/postfix/default.nix
index 694d7044b8a..0b6ed49737d 100644
--- a/pkgs/servers/mail/postfix/default.nix
+++ b/pkgs/servers/mail/postfix/default.nix
@@ -12,7 +12,7 @@ let
     "-DUSE_TLS" "-DUSE_SASL_AUTH" "-DUSE_CYRUS_SASL" "-I${cyrus_sasl.dev}/include/sasl"
     "-DHAS_DB_BYPASS_MAKEDEFS_CHECK"
    ] ++ lib.optional withPgSQL "-DHAS_PGSQL"
-     ++ lib.optionals withMySQL [ "-DHAS_MYSQL" "-I${libmysqlclient}/include/mysql" "-L${libmysqlclient}/lib/mysql" ]
+     ++ lib.optionals withMySQL [ "-DHAS_MYSQL" "-I${libmysqlclient.dev}/include/mysql" "-L${libmysqlclient}/lib/mysql" ]
      ++ lib.optional withSQLite "-DHAS_SQLITE"
      ++ lib.optionals withLDAP ["-DHAS_LDAP" "-DUSE_LDAP_SASL"]);
    auxlibs = lib.concatStringsSep " " ([