diff --git a/src/libsm64.h b/src/libsm64.h
index 3dbf3a6..6274477 100644
--- a/src/libsm64.h
+++ b/src/libsm64.h
@@ -75,7 +75,7 @@ extern SM64_LIB_FN void sm64_global_terminate( void );
 extern SM64_LIB_FN void sm64_static_surfaces_load( const struct SM64Surface *surfaceArray, uint32_t numSurfaces );
 
 extern SM64_LIB_FN int32_t sm64_mario_create( int16_t x, int16_t y, int16_t z );
-extern SM64_LIB_FN void sm64_mario_tick( uint32_t marioId, const struct SM64MarioInputs *inputs, struct SM64MarioState *outState, struct SM64MarioGeometryBuffers *outBuffers );
+extern SM64_LIB_FN void sm64_mario_tick( int32_t marioId, const struct SM64MarioInputs *inputs, struct SM64MarioState *outState, struct SM64MarioGeometryBuffers *outBuffers );
 extern SM64_LIB_FN void sm64_mario_delete( int32_t marioId );
 
 extern SM64_LIB_FN uint32_t sm64_surface_object_create( const struct SM64SurfaceObject *surfaceObject );