diff --git a/src/collision/collision_util.f90 b/src/collision/collision_util.f90
index 21242c1d5..728a8ac24 100644
--- a/src/collision/collision_util.f90
+++ b/src/collision/collision_util.f90
@@ -493,6 +493,7 @@ module subroutine collision_util_setup_fragments(self, n)
 
       allocate(swiftest_particle_info :: self%info(n))
 
+      allocate(self%id(n))
       allocate(self%status(n))
       allocate(self%rh(NDIM, n))
       allocate(self%vh(NDIM, n))