diff --git a/lib/faker.rb b/lib/faker.rb
index a5d7d472b9..c0c5708541 100644
--- a/lib/faker.rb
+++ b/lib/faker.rb
@@ -58,6 +58,9 @@ class Base
     ULetters = Array('A'..'Z')
     LLetters = Array('a'..'z')
     Letters = ULetters + LLetters
+    # Frozen digit strings, used to avoid allocating a new string for each
+    # random digit generated by #numerify.
+    DIGITS = %w[0 1 2 3 4 5 6 7 8 9].freeze
 
     class << self
       attr_reader :flexible_key
@@ -66,9 +69,15 @@ class << self
 
       ## by default numerify results do not start with a zero
       def numerify(number_string, leading_zero: false)
-        return number_string.gsub('#') { rand(10).to_s } if leading_zero
-
-        number_string.sub('#') { rand(1..9).to_s }.gsub('#') { rand(10).to_s }
+        leading = !leading_zero
+        number_string.gsub('#') do
+          if leading
+            leading = false
+            DIGITS[rand(1..9)]
+          else
+            DIGITS[rand(10)]
+          end
+        end
       end
 
       def letterify(letter_string)