diff --git a/applications/lofar2/designs/lofar2_unb2b_beamformer/lofar2_unb2b_beamformer.mmap.gold b/applications/lofar2/designs/lofar2_unb2b_beamformer/lofar2_unb2b_beamformer.mmap.gold
index ae1a70b3986901025ae0c3a48f5b42bde0470b4b..c92f08599cc8e1bc8974564f4843ca59843095d4 100644
--- a/applications/lofar2/designs/lofar2_unb2b_beamformer/lofar2_unb2b_beamformer.mmap.gold
+++ b/applications/lofar2/designs/lofar2_unb2b_beamformer/lofar2_unb2b_beamformer.mmap.gold
@@ -1,5 +1,9 @@
 fpga_name = lofar2_unb2b_beamformer
 number_of_columns = 11
+# There can be multiple lines with a single key. The host should ignore unknown keys.
+# The lines with columns follow after the number_of_columns keys. The host should ignore
+# the extra columns in case the mmap contains more columns than the host expects.
+#
 # col 1: mm_port_name, if - then it is part of previous MM port.
 # col 2: number of peripherals, if - then it is part of previous peripheral.
 # col 3: number of mm_ports, if - then it is part of previous MM port.