diff --git a/sf/sf_h5_writer.cpp b/sf/sf_h5_writer.cpp
index e4d57f8..2e7bd7f 100644
--- a/sf/sf_h5_writer.cpp
+++ b/sf/sf_h5_writer.cpp
@@ -14,7 +14,8 @@ int main (int argc, char *argv[])
     if (argc != 10 && argc != 11) {
         cout << endl;
         cout << "Usage: sf_h5_writer [connection_address] [output_file] [n_frames]";
-        cout << " [rest_port] [user_id] [bsread_address] [n_modules] [n_bad_modules] [detector_name]" << endl;
+        cout << " [rest_port] [user_id] [bsread_address] [n_modules] [n_bad_modules] [detector_name]";
+        cout << " [frames_per_file]" << endl;
         cout << "\tconnection_address: Address to connect to the stream (PULL). Example: tcp://127.0.0.1:40000" << endl;
         cout << "\toutput_file: Name of the output file." << endl;
         cout << "\tn_frames: Number of images to acquire. 0 for infinity (until /stop is called)." << endl;