diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index bcdd32a..d90f29e 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -1947,6 +1947,9 @@ rb_deflate_params(VALUE obj, VALUE v_level, VALUE v_strategy)
     level = ARG_LEVEL(v_level);
     strategy = ARG_STRATEGY(v_strategy);
 
+    if (NIL_P(z->buf) || z->stream.avail_out == 0) {
+	zstream_expand_buffer(z);
+    }
     n = z->stream.avail_out;
     err = deflateParams(&z->stream, level, strategy);
     filled = n - z->stream.avail_out;
diff --git a/test/zlib/test_zlib.rb b/test/zlib/test_zlib.rb
index e1ecbf8..970fbba 100644
--- a/test/zlib/test_zlib.rb
+++ b/test/zlib/test_zlib.rb
@@ -216,6 +216,20 @@ def test_params
       z.close # without this, outputs `zlib(finalizer): the stream was freed prematurely.'
     end
 
+    def test_params_without_output_buffer
+      z = Zlib::Deflate.new
+      z.params(Zlib::BEST_SPEED, Zlib::DEFAULT_STRATEGY)
+      z << "foo"
+      assert_equal("foo", Zlib::Inflate.inflate(z.finish))
+
+      z = Zlib::Deflate.new
+      z << "foo"
+      s = z.flush_next_out
+      z.params(Zlib::BEST_COMPRESSION, Zlib::FILTERED)
+      z << "bar"
+      assert_equal("foobar", Zlib::Inflate.inflate(s + z.finish))
+    end
+
     def test_set_dictionary
       z = Zlib::Deflate.new
       z.set_dictionary("foo")