diff --git a/lib/webmock/http_lib_adapters/http_rb/request.rb b/lib/webmock/http_lib_adapters/http_rb/request.rb
index 078be318..32b36b7f 100644
--- a/lib/webmock/http_lib_adapters/http_rb/request.rb
+++ b/lib/webmock/http_lib_adapters/http_rb/request.rb
@@ -3,11 +3,21 @@
 module HTTP
   class Request
     def webmock_signature
-      request_body = if defined?(HTTP::Request::Body)
-                       String.new.tap { |string| body.each { |part| string << part } }
-                     else
-                       body
-                     end
+      request_body = nil
+
+      if defined?(HTTP::Request::Body)
+        request_body = String.new
+        first_chunk_encoding = nil
+        body.each do |part|
+          request_body << part
+          first_chunk_encoding ||= part.encoding
+        end
+
+        request_body.force_encoding(first_chunk_encoding) if first_chunk_encoding
+        request_body
+      else
+        request_body = body
+      end
 
       ::WebMock::RequestSignature.new(verb, uri.to_s, {
         headers: headers.to_h,
diff --git a/spec/acceptance/http_rb/http_rb_spec.rb b/spec/acceptance/http_rb/http_rb_spec.rb
index 097e7760..409f4b63 100644
--- a/spec/acceptance/http_rb/http_rb_spec.rb
+++ b/spec/acceptance/http_rb/http_rb_spec.rb
@@ -90,4 +90,12 @@
       response.connection.close
     end
   end
+
+  it "should preserve request body encoding when matching requests" do
+    stub_request(:post, "www.example.com").with(body: (lambda {|body|
+      body.encoding == Encoding::UTF_8
+    }))
+    http_request(:post, "http://www.example.com/", body: "abc")
+  end
+
 end