diff --git a/src/api/l_physics_shapes.c b/src/api/l_physics_shapes.c
index d133291f..2d9f49a8 100644
--- a/src/api/l_physics_shapes.c
+++ b/src/api/l_physics_shapes.c
@@ -402,7 +402,7 @@ static int l_lovrCompoundShapeAddShape(lua_State* L) {
 
 static int l_lovrCompoundShapeReplaceShape(lua_State* L) {
   CompoundShape* shape = luax_checktype(L, 1, CompoundShape);
-  uint32_t index = luax_checku32(L, 2);
+  uint32_t index = luax_checku32(L, 2) - 1;
   Shape* child = luax_checkshape(L, 3);
   float position[3], orientation[4];
   int i = 4;
diff --git a/src/modules/physics/physics_jolt.c b/src/modules/physics/physics_jolt.c
index 7b778dca..2f2aa1cb 100644
--- a/src/modules/physics/physics_jolt.c
+++ b/src/modules/physics/physics_jolt.c
@@ -1041,6 +1041,7 @@ void lovrCompoundShapeReplaceShape(CompoundShape* shape, uint32_t index, Shape*
   lovrCheck(child != shape, "Don't put a CompoundShape inside itself!  lol");
   JPH_Vec3 pos = { position[0], position[1], position[2] };
   JPH_Quat rot = { orientation[0], orientation[1], orientation[2], orientation[3] };
+  lovrRelease(lovrCompoundShapeGetShape(shape, index), lovrShapeDestroy);
   JPH_MutableCompoundShape_ModifyShape2((JPH_MutableCompoundShape*) shape->shape, index, &pos, &rot, child->shape);
   lovrRetain(child);
 }