diff --git a/logstash-core/lib/logstash/config/mixin.rb b/logstash-core/lib/logstash/config/mixin.rb
index fd2d71e85..a93cac08b 100644
--- a/logstash-core/lib/logstash/config/mixin.rb
+++ b/logstash-core/lib/logstash/config/mixin.rb
@@ -38,8 +38,7 @@ module LogStash::Config::Mixin
   PLUGIN_VERSION_1_0_0 = LogStash::Util::PluginVersion.new(1, 0, 0)
   PLUGIN_VERSION_0_9_0 = LogStash::Util::PluginVersion.new(0, 9, 0)
 
-  ENV_PLACEHOLDER_REGEX = Regexp.new(/\$\w+|\$\{\w+(\:[^}]*)?\}/)
-
+  ENV_PLACEHOLDER_REGEX = /\$(?<name>\w+)|\$\{(?<name>\w+)(\:(?<default>[^}]*))?\}/
 
   # This method is called when someone does 'include LogStash::Config'
   def self.included(base)
@@ -149,37 +148,24 @@ module LogStash::Config::Mixin
   # Replace all environment variable references in 'value' param by environment variable value and return updated value
   # Process following patterns : $VAR, ${VAR}, ${VAR:defaultValue}
   def replace_env_placeholders(value)
-    if (value.is_a?(String))
-      while value =~ ENV_PLACEHOLDER_REGEX
-        valueParts = value.partition(ENV_PLACEHOLDER_REGEX)
-        placeHolder = valueParts[1]
-        if placeHolder.start_with?("${")
-          envVarName = placeHolder.slice(2..placeHolder.length - 2)
-        else
-          envVarName = placeHolder.slice(1..placeHolder.length - 1)
-        end
-        if envVarName.include?(':')
-          placeHolderParts = envVarName.split(':')
-          envVarName = placeHolderParts[0]
-          defaultValue = placeHolderParts[1] || ""
-        else
-          defaultValue = ""
-        end
+    return value unless value.is_a?(String)
+    #raise ArgumentError, "Cannot replace ENV placeholders on non-strings. Got #{value.class}" if !value.is_a?(String)
 
-        envVarValue = ENV[envVarName]
-        if envVarValue.nil?
-          envVarValue = defaultValue
-          if defaultValue.empty?
-            @logger.warn("In plugin '#{self.class.config_name}', " +
-                         "referenced environment variable '#{envVarName}' does not exist. " +
-                         "This reference has been replaced by empty string.")
-          end
-        end
-        value = valueParts[0] << envVarValue << valueParts[2]
-        @logger.info("Replacing config environment variable '#{placeHolder}' with #{envVarValue}")
-      end
+    value.gsub(ENV_PLACEHOLDER_REGEX) do |placeholder|
+      # Note: Ruby docs claim[1] Regexp.last_match is thread-local and scoped to
+      # the call, so this should be thread-safe.
+      #
+      # [1] http://ruby-doc.org/core-2.1.1/Regexp.html#method-c-last_match
+      name = Regexp.last_match(:name)
+      default = Regexp.last_match(:default)
+
+      replacement = ENV.fetch(name, default)
+      #if replacement.nil?
+        #raise LogStash::ConfigurationError, "Cannot evaluate `#{placeholder}`. Environment variable `#{name}` is not set and there is no default value given."
+      #end
+      @logger.info? && @logger.info("Replacing config environment variable '#{placeholder}' with `#{replacement}`")
+      replacement
     end
-    return value
   end # def replace_env_placeholders
 
   module DSL