diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4f6d8240..91516c79 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,20 +1,18 @@
 # CHANGELOG
 
-## 0.9.0 - UNRELEASED
+## 0.9.0 - 2022-03-25
 
 Requires Panda system version >= 4.2.1
 
-  * **BREAKING** Add `O_ddP_O` base acceleration to robot state
-  * **BREAKING** New `base_acceleration_initialization_timeout` & `base_acceleration_invalid_reading` reflexes
-
-## 0.8.1 - UNRELEASED
-
-Requires Panda system version >= 4.0.0
-
+ * **BREAKING** Add `O_ddP_O` base acceleration to robot state, harcoded to `{0, 0, -9.81}`.
+ * **BREAKING** New `base_acceleration_initialization_timeout`, `base_acceleration_invalid_reading`
+                `cartesian_spline_motion_generator_violation` and 
+                `joint_via_motion_generator_planning_joint_limit_violation` reflexes.
  * Adjust network error messages. Distinguish between problems resulting from:
     - a wrong network configuration. A message is shown after a timeout of 60 seconds.
     - a missing FCI feature or a blocked port due to Single Point of Control. An immediate error
       response is shown.
+ * Changed signature of `franka::Model::gravity` to use `O_ddP_O` in the robot state.
 
 ## 0.8.0 - 2020-04-29
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bccb29a9..f0d3da7c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.4)
 project(libfranka
-  VERSION 0.8.1
+  VERSION 0.9.0
   LANGUAGES CXX
 )
 
diff --git a/include/franka/model.h b/include/franka/model.h
index 54532093..99218b1d 100644
--- a/include/franka/model.h
+++ b/include/franka/model.h
@@ -263,13 +263,20 @@ class Model {
    *
    * @param[in] robot_state State from which the gravity vector should be calculated.
    * @param[in] gravity_earth Earth's gravity vector. Unit: \f$\frac{m}{s^2}\f$.
-   * Default to {0.0, 0.0, -9.81}.
    *
    * @return Gravity vector.
    */
   std::array<double, 7> gravity(const franka::RobotState& robot_state,
-                                const std::array<double, 3>& gravity_earth = {
-                                    {0., 0., -9.81}}) const noexcept;
+                                const std::array<double, 3>& gravity_earth) const noexcept;
+
+  /**
+   * Calculates the gravity vector using the robot state. Unit: \f$[Nm]\f$.
+   *
+   * @param[in] robot_state State from which the gravity vector should be calculated.
+   *
+   * @return Gravity vector.
+   */
+  std::array<double, 7> gravity(const franka::RobotState& robot_state) const noexcept;
 
   /// @cond DO_NOT_DOCUMENT
   Model(const Model&) = delete;
diff --git a/include/franka/robot_state.h b/include/franka/robot_state.h
index 452bb569..9f92773c 100644
--- a/include/franka/robot_state.h
+++ b/include/franka/robot_state.h
@@ -331,6 +331,7 @@ struct RobotState {
    * Linear component of the acceleration of the robot's base, expressed in frame parallel to the
    * @ref o-frame "base frame", i.e. the base's translational acceleration. If the base is resting
    * this shows the direction of the gravity vector.
+   * It is harcoded for now to `{0, 0, -9.81}`.
    */
   std::array<double, 3> O_ddP_O{};  // NOLINT(readability-identifier-naming)
 
diff --git a/src/model.cpp b/src/model.cpp
index bd019115..a53f1bac 100644
--- a/src/model.cpp
+++ b/src/model.cpp
@@ -228,6 +228,10 @@ std::array<double, 7> franka::Model::gravity(const franka::RobotState& robot_sta
   return gravity(robot_state.q, robot_state.m_total, robot_state.F_x_Ctotal, gravity_earth);
 };
 
+std::array<double, 7> franka::Model::gravity(const franka::RobotState& robot_state) const noexcept {
+  return gravity(robot_state, robot_state.O_ddP_O);
+};
+
 std::array<double, 7> franka::Model::gravity(
     const std::array<double, 7>& q,
     double m_total,