2 files changed, 12 insertions, 3 deletions
diff --git a/activesupport/lib/active_support/core_ext/object/blank.rb b/activesupport/lib/active_support/core_ext/object/blank.rb
index e42ad852dd..2ca431ab10 100644
--- a/activesupport/lib/active_support/core_ext/object/blank.rb
+++ b/activesupport/lib/active_support/core_ext/object/blank.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/regexp"
+require "concurrent/map"
 
 class Object
   # An object is blank if it's false, empty, or a whitespace string.
@@ -102,6 +103,9 @@ end
 
 class String
   BLANK_RE = /\A[[:space:]]*\z/
+  ENCODED_BLANKS = Concurrent::Map.new do |h, enc|
+    h[enc] = Regexp.new(BLANK_RE.source.encode(enc), BLANK_RE.options | Regexp::FIXEDENCODING)
+  end
 
   # A string is blank if it's empty or contains whitespaces only:
   #
@@ -119,7 +123,12 @@ class String
     # The regexp that matches blank strings is expensive. For the case of empty
     # strings we can speed up this method (~3.5x) with an empty? call. The
     # penalty for the rest of strings is marginal.
-    empty? || BLANK_RE.match?(self)
+    empty? ||
+      begin
+        BLANK_RE.match?(self)
+      rescue Encoding::CompatibilityError
+        ENCODED_BLANKS[self.encoding].match?(self)
+      end
   end
 end
 
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb
index 1744a44df6..9bb99087bc 100644
--- a/activesupport/lib/active_support/core_ext/object/duplicable.rb
+++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb
@@ -108,8 +108,8 @@ require "bigdecimal"
 class BigDecimal
   # BigDecimals are duplicable:
   #
-  #   BigDecimal.new("1.2").duplicable? # => true
-  #   BigDecimal.new("1.2").dup         # => #<BigDecimal:...,'0.12E1',18(18)>
+  #   BigDecimal("1.2").duplicable? # => true
+  #   BigDecimal("1.2").dup         # => #<BigDecimal:...,'0.12E1',18(18)>
   def duplicable?
     true
   end