diff --git a/lib/httpx/response.rb b/lib/httpx/response.rb
index e30ba8fa..e4f0891e 100644
--- a/lib/httpx/response.rb
+++ b/lib/httpx/response.rb
@@ -134,18 +134,28 @@ module HTTPX
       end
 
       def to_s
-        rewind
-        if @buffer
+        case @buffer
+        when StringIO
+          begin
+            @buffer.string.force_encoding(@encoding)
+          rescue ArgumentError
+            @buffer.string
+          end
+        when Tempfile, File
+          rewind
           content = @buffer.read
           begin
-            return content.force_encoding(@encoding)
+            content.force_encoding(@encoding)
           rescue ArgumentError # ex: unknown encoding name - utf
-            return content
+            content
+          ensure
+            close
           end
+        when nil
+          "".b
+        else
+          @buffer
         end
-        "".b
-      ensure
-        close
       end
       alias_method :to_str, :to_s
 
diff --git a/test/response_test.rb b/test/response_test.rb
index b7c042ef..ea974cbf 100644
--- a/test/response_test.rb
+++ b/test/response_test.rb
@@ -43,6 +43,7 @@ class ResponseTest < Minitest::Test
 
   def test_response_body_to_s
     body1 = Response::Body.new(Response.new(request, 200, "2.0", {}), Options.new(body_threshold_size: 1024))
+    assert body1 == "", "body should be empty"
     assert body1.empty?, "body must be empty after initialization"
     body1.write("foo")
     assert body1 == "foo", "body must be updated"
@@ -62,6 +63,11 @@ class ResponseTest < Minitest::Test
     body4.write(text)
     req_text = body4.to_s
     assert text == req_text, "request body must be in original encoding (#{req_text})"
+
+    payload = "a" * 2048
+    body5 = Response::Body.new(Response.new(request, 200, "2.0", {}), Options.new(body_threshold_size: 1024))
+    body5.write(payload)
+    assert body5 == "a" * 2048, "body messed up with file"
   end
 
   def test_response_body_copy_to_memory