diff --git a/rclcpp_action/include/rclcpp_action/exceptions.hpp b/rclcpp_action/include/rclcpp_action/exceptions.hpp
index 15bb165..33d94c2 100644
--- a/rclcpp_action/include/rclcpp_action/exceptions.hpp
+++ b/rclcpp_action/include/rclcpp_action/exceptions.hpp
@@ -25,7 +25,7 @@ class UnknownGoalHandleError : public std::invalid_argument
 {
 public:
   UnknownGoalHandleError()
-  : std::invalid_argument("Goal handle is not know to this client.")
+  : std::invalid_argument("Goal handle is not known to this client.")
   {
   }
 };