diff --git a/lib/pbbuilder.rb b/lib/pbbuilder.rb
index 1ff2c65..8a4198a 100644
--- a/lib/pbbuilder.rb
+++ b/lib/pbbuilder.rb
@@ -53,7 +53,7 @@ def set!(field, *args, &block)
     descriptor = _descriptor_for_field(name)
     ::Kernel.raise ::ArgumentError, "Unknown field #{name}" if descriptor.nil?
 
-    if block
+    if ::Kernel.block_given?
       ::Kernel.raise ::ArgumentError, "can't pass block to non-message field" unless descriptor.type == :message
 
       if descriptor.label == :repeated
@@ -61,13 +61,12 @@ def set!(field, *args, &block)
         ::Kernel.raise ::ArgumentError, "wrong number of arguments #{args.length} (expected 1)" unless args.length == 1
         collection = args.first
         _append_repeated(name, descriptor, collection, &block)
-        return
+      else
+        # pb.field { pb.name "hello" }
+        ::Kernel.raise ::ArgumentError, "wrong number of arguments (expected 0)" unless args.empty?
+        message = (@message[name] ||= _new_message_from_descriptor(descriptor))
+        _scope(message, &block)
       end
-
-      ::Kernel.raise ::ArgumentError, "wrong number of arguments (expected 0)" unless args.empty?
-      # pb.field { pb.name "hello" }
-      message = (@message[name] ||= _new_message_from_descriptor(descriptor))
-      _scope(message, &block)
     elsif args.length == 1
       arg = args.first
       if descriptor.label == :repeated
@@ -123,11 +122,11 @@ def extract!(element, *args)
   def merge!(object)
     ::Kernel.raise Pbbuilder::MergeError.build(target!, object) unless object.class == ::Hash
 
-    object.each_key do |key|
-      next if object[key].respond_to?(:empty?) && object[key].empty?
+    object.each do |key, value|
+      next if value.respond_to?(:empty?) && value.empty?
 
       descriptor = _descriptor_for_field(key)
-      ::Kernel.raise ::ArgumentError, "Unknown field #{name}" if descriptor.nil?
+      ::Kernel.raise ::ArgumentError, "Unknown field #{key}" if descriptor.nil?
 
       if descriptor.label == :repeated
         # optional empty fields don't show up in @message object,
@@ -136,48 +135,48 @@ def merge!(object)
           @message[key.to_s] = _new_message_from_descriptor(descriptor)
         end
 
-        if object[key].respond_to?(:to_hash)
-          object[key].to_hash.each {|k, v| @message[key.to_s][k] = v}
-        elsif object[key].respond_to?(:to_ary)
-          elements = object[key].map do |obj|
+        if value.respond_to?(:to_hash)
+          value.to_hash.each {|k, v| @message[key.to_s][k] = v}
+        elsif value.respond_to?(:to_ary)
+          elements = value.map do |obj|
             descriptor.subtype ? descriptor.subtype.msgclass.new(obj) : obj
           end
 
           @message[key.to_s].replace(elements)
         end
       else
-        if object[key].class == ::String
+        if value.class == ::String
           # pb.fields {"one" => "two"}
-          @message[key.to_s] = object[key]
-        elsif object[key].class == ::TrueClass || object[key].class == ::FalseClass
+          @message[key.to_s] = value
+        elsif value.class == ::TrueClass || value.class == ::FalseClass
           # pb.boolean true || false
-          @message[key.to_s] = object[key]
-        elsif object[key].class == ::Array
+          @message[key.to_s] = value
+        elsif value.class == ::Array
           # pb.field_name do
           #    pb.tags ["ok", "cool"]
           # end
 
-          @message[key.to_s] = object[key]
-        elsif object[key].class == ::Hash
+          @message[key.to_s] = value
+        elsif descriptor.type == :message
           if @message[key.to_s].nil?
             @message[key.to_s] = _new_message_from_descriptor(descriptor)
           end
 
-          object[key].each do |k, v|
-            if object[key][k].respond_to?(:to_hash)
+          value.each do |k, v|
+            if value[k].respond_to?(:to_hash)
               if @message[key.to_s][k.to_s].nil?
                 descriptor = @message[key.to_s].class.descriptor.lookup(k.to_s)
                 @message[key.to_s][k.to_s] = _new_message_from_descriptor(descriptor)
               end
 
-              _scope(@message[key.to_s][k.to_s]) { self.merge!(object[key][k]) }
-            elsif object[key][k].respond_to?(:to_ary)
-              @message[key.to_s][k.to_s].replace object[key][k]
+              _scope(@message[key.to_s][k.to_s]) { self.merge!(value[k]) }
+            elsif value[k].respond_to?(:to_ary)
+              @message[key.to_s][k.to_s].replace value[k]
             else
               # Throws an error, if we try to merge nil object into empty value.
-              next if object[key][k].nil? && @message[key.to_s][k.to_s].nil?
+              next if value[k].nil? && @message[key.to_s][k.to_s].nil?
 
-              @message[key.to_s][k.to_s] = object[key][k]
+              @message[key.to_s][k.to_s] = value[k]
             end
           end
         end