diff --git a/Cargo.toml b/Cargo.toml
index 2b76f12..e3c6866 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,4 +19,4 @@ sdl2 = "^0.32"
 crossbeam-channel = "^0.4"
 structopt = "^0.3"
 # example: ffmpeg_recorder
-ffmpeg4 = "*"
+ffmpeg4 = "0.4.0"
diff --git a/examples/sdl2_emulator.rs b/examples/sdl2_emulator.rs
index 71a0a0f..e0c54ed 100644
--- a/examples/sdl2_emulator.rs
+++ b/examples/sdl2_emulator.rs
@@ -230,7 +230,7 @@ impl MyEmulator {
         }
     }
 
-    fn input_state_keyboard(&mut self, port: u32, device: &InputDeviceId, index: &InputIndex) -> i16 {
+    fn input_state_keyboard(&mut self, port: u32, device: &InputDeviceId, _index: &InputIndex) -> i16 {
         if port != 0 { // Keyboard only controls the first port.
             return 0;
         }