diff --git a/MantleAPI/include/MantleAPI/Traffic/entity_helper.h b/MantleAPI/include/MantleAPI/Traffic/entity_helper.h
index 608e879cc7096dda6032bb84a5f3d7b5a88d1a6f..0c65ca40b0707fb757d55575d590ebcdef46a064 100644
--- a/MantleAPI/include/MantleAPI/Traffic/entity_helper.h
+++ b/MantleAPI/include/MantleAPI/Traffic/entity_helper.h
@@ -21,7 +21,7 @@
 
 namespace mantle_api
 {
-void SetSpeed(mantle_api::IEntity* entity, double velocity)
+inline void SetSpeed(mantle_api::IEntity* entity, double velocity)
 {
   auto orientation = entity->GetOrientation();