diff --git a/src/simulation.cpp b/src/simulation.cpp
index 679cabb..4c8657e 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -85,9 +85,22 @@ void update_simulation(SimulationState* sim) {
 
         int new_parent = find_dominant_body(sim, i);
         if (new_parent != body->parent_index && new_parent != -1) {
-            // FIXME: there's now a bug here when changing parent bodes
-            //  I think it's that the local position is never updated
+            // Convert current local coordinates to global coordinates using old parent
+            if (body->parent_index >= 0 && body->parent_index < sim->body_count) {
+                CelestialBody* old_parent = &sim->bodies[body->parent_index];
+                body->position = vec3_add(body->local_position, old_parent->position);
+                body->velocity = vec3_add(body->local_velocity, old_parent->velocity);
+            }
+            
+            // Update parent index
             body->parent_index = new_parent;
+            
+            // Convert global coordinates to local coordinates using new parent
+            if (body->parent_index >= 0 && body->parent_index < sim->body_count) {
+                CelestialBody* new_parent_body = &sim->bodies[body->parent_index];
+                body->local_position = vec3_sub(body->position, new_parent_body->position);
+                body->local_velocity = vec3_sub(body->velocity, new_parent_body->velocity);
+            }
         }
 
         if (body->parent_index >= 0 && body->parent_index < sim->body_count) {
@@ -109,7 +122,7 @@ static void compute_orbital_velocity_from_vis_viva(CelestialBody* body,
                                                      CelestialBody* parent) {
     Vec3 r = vec3_sub(body->position, parent->position);
     double distance = vec3_magnitude(r);
-    double e = body->eccentricity;
+    // double e = body->eccentricity; // FIXME: unused variable
     double a = body->semi_major_axis;
     double v_squared = G * parent->mass * (2.0 / distance - 1.0 / a);
     // FIXME: need error handling here