diff --git a/config.mk.in b/config.mk.in
index 938f0c9..85ba445 100644
--- a/config.mk.in
+++ b/config.mk.in
@@ -95,9 +95,14 @@ JSON_INDENT ?= no
 CONFIGFILE = /etc/default/ot-recorder
 
 # Optionally specify the path to the Mosquitto libs, include here
+# ...
 MOSQUITTO_CFLAGS = `$(PKG_CONFIG) --cflags libmosquitto`    #  libcjson
 MOSQUITTO_LIBS   = `$(PKG_CONFIG) --libs libmosquitto`      #  libcjson
 
+# ... for Mosquitto 2.1 also needs libcjson
+# MOSQUITTO_CFLAGS = `$(PKG_CONFIG) --cflags libmosquitto libcjson`
+# MOSQUITTO_LIBS   = `$(PKG_CONFIG) --libs libmosquitto libcjson`
+
 # Milliseconds (ms) timeout for reverse geocoding
 GEOCODE_TIMEOUT = 4000