diff --git a/lib/rackstash/logger.rb b/lib/rackstash/logger.rb
index ac9636f..4a51425 100644
--- a/lib/rackstash/logger.rb
+++ b/lib/rackstash/logger.rb
@@ -57,13 +57,24 @@ module Rackstash
     #   By default we use {PROGNAME}.
     # @param formatter [#call] the log formatter for each individual buffered
     #   line. See {#formatter} for details.
-    def initialize(*flows, level: DEBUG, progname: PROGNAME, formatter: Formatter.new)
+    # @yieldparam flow [Rackstash::Flow] if the given block accepts an argument,
+    #   we yield the last {Flow} as a parameter. Without an expected argument,
+    #   the block is directly executed in the context of the last {Flow}.
+    def initialize(*flows, level: DEBUG, progname: PROGNAME, formatter: Formatter.new, &block)
       @buffer_stack = Concurrent::ThreadLocalVar.new
 
       @sink = Rackstash::Sink.new(*flows)
       self.level = level
       self.progname = progname
       self.formatter = formatter
+
+      if block_given? && (flow = @sink.flows.last)
+        if block.arity == 0
+          flow.instance_eval(&block)
+        else
+          yield flow
+        end
+      end
     end
 
     # Add a message to the current buffer without any further formatting. If
diff --git a/spec/rackstash/logger_spec.rb b/spec/rackstash/logger_spec.rb
index d008434..a523451 100644
--- a/spec/rackstash/logger_spec.rb
+++ b/spec/rackstash/logger_spec.rb
@@ -35,6 +35,35 @@ describe Rackstash::Logger do
       logger = described_class.new('output.log', formatter: -> {})
       expect(logger.formatter).to be_a Proc
     end
+
+    it 'yields the last flow to a parameterized block' do
+      block_called = 0
+      block_self = nil
+      block_args = nil
+
+      described_class.new(StringIO.new, StringIO.new) do |*args|
+        block_called += 1
+        block_self = self
+        block_args = args
+      end
+
+      expect(block_called).to eql 1
+      expect(block_self).to equal self
+      expect(block_args).to match [instance_of(Rackstash::Flow)]
+    end
+
+    it 'instance_evals the parameter-less block in the last flow' do
+      block_called = 0
+      block_self = nil
+
+      described_class.new(StringIO.new, StringIO.new) do
+        block_called += 1
+        block_self = self
+      end
+
+      expect(block_called).to eql 1
+      expect(block_self).to be_instance_of(Rackstash::Flow)
+    end
   end
 
   describe 'subscript accessors' do