--- ext/numru/extconf.rb.orig	2026-04-30 17:48:26 UTC
+++ ext/numru/extconf.rb
@@ -51,7 +51,7 @@ ncver = ncversion.gsub(/\./,'')
 
 ncver0 = ncversion[0..0]  # "3" or "4"
 ncver = ncversion.gsub(/\./,'')
-unless /^\d\d\d$/ =~ ncver   # 3 digits
+unless /^\d{3,4}$/ =~ ncver  # 3 or 4 digits
   raise("Invalid netcdf version: #{ncversion}. Use --with-netcdf-version=") 
 end
 $CFLAGS += ' -DNCVER='+ncver