--- a/SL/Helper/UNECERecommendation20.pm
+++ b/SL/Helper/UNECERecommendation20.pm
@@ -36,6 +36,9 @@ my @mappings = (
   [ 'MLT', qr{^(?:ml|milli *liter|milli *litre)$}i ],
   [ 'LTR', qr{^(?:l|liter|litre)$}i ],
 
+  # cubic volumes
+  [ 'MTQ', qr{^(?:m³|cbm|kubik *meter|kubik *metre|cubic *meter|cubic *metre)$}i ],
+
   # miscellaneous
   [ 'C62', qr{^(?:stck|stück|pieces?|pc|psch|pauschal)$}i ],
 );