diff --git a/src/drivers/l3gd20/l3gd20.cpp b/src/drivers/l3gd20/l3gd20.cpp
index f8cd509a2e..cad3ff9378 100644
--- a/src/drivers/l3gd20/l3gd20.cpp
+++ b/src/drivers/l3gd20/l3gd20.cpp
@@ -982,6 +982,7 @@ namespace l3gd20
 
 L3GD20	*g_dev;
 
+void	l3gd20_usage();
 void	start(bool external_bus, enum Rotation rotation);
 void	test();
 void	reset();