diff --git a/lib/membrane_rtsp/request.ex b/lib/membrane_rtsp/request.ex
index 228b596..9ff81d2 100644
--- a/lib/membrane_rtsp/request.ex
+++ b/lib/membrane_rtsp/request.ex
@@ -69,6 +69,8 @@ defmodule Membrane.RTSP.Request do
   "DESCRIBE rtsp://domain.net:554/path:movie.mov RTSP/1.0\\r\\n\\r\\n"
   iex> Request.stringify(%Request{method: "PLAY", path: "trackID=2"}, uri)
   "PLAY rtsp://domain.net:554/path:movie.mov/trackID=2 RTSP/1.0\\r\\n\\r\\n"
+  iex> Request.stringify(%Request{method: "SET_PARAMETER", body: "parameter:value"}, uri)
+  "SET_PARAMETER rtsp://domain.net:554/path:movie.mov RTSP/1.0\\r\\n\\r\\nparameter:value"
 
   ```
 
@@ -89,7 +91,8 @@ defmodule Membrane.RTSP.Request do
       process_uri(request, uri),
       " RTSP/1.0",
       render_headers(headers),
-      "\r\n\r\n"
+      "\r\n\r\n",
+      request.body
     ])
   end
 
diff --git a/lib/membrane_rtsp/session/logic.ex b/lib/membrane_rtsp/session/logic.ex
index d1a8a86..2b2463e 100644
--- a/lib/membrane_rtsp/session/logic.ex
+++ b/lib/membrane_rtsp/session/logic.ex
@@ -50,6 +50,7 @@ defmodule Membrane.RTSP.Logic do
 
     request
     |> inject_session_header(session_id)
+    |> inject_content_length()
     |> Request.with_header("CSeq", cseq |> to_string())
     |> Request.with_header("User-Agent", @user_agent)
     |> apply_credentials(uri, state.auth)
@@ -65,6 +66,14 @@ defmodule Membrane.RTSP.Logic do
     end
   end
 
+  @spec inject_content_length(Request.t()) :: Request.t()
+  def inject_content_length(request) do
+    case request.body do
+      "" -> request
+      body -> Request.with_header(request, "Content-Length", to_string(byte_size(body)))
+    end
+  end
+
   @spec apply_credentials(Request.t(), URI.t(), State.auth_t()) :: Request.t()
   def apply_credentials(request, %URI{userinfo: nil}, _auth_options), do: request