diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 5e95d2e5a5..60ef249e37 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -92,7 +92,7 @@ module ActiveSupport
       return camel_cased_word unless camel_cased_word =~ /[A-Z-]|::/
       word = camel_cased_word.to_s.gsub('::'.freeze, '/'.freeze)
       word.gsub!(/(?:(?<=([A-Za-z\d]))|\b)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1 && '_'.freeze }#{$2.downcase}" }
-      word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, ' \1_\2'.freeze)
+      word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
       word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
       word.tr!("-".freeze, "_".freeze)
       word.downcase!