diff --git a/src/gravity/Default/gravity_part.h b/src/gravity/Default/gravity_part.h
index 06b9c52e14a655aa97b6c36ff9dca1f1cdd6e9a0..ef93488f0b788064e2f897ae9c84f05c371b0e12 100644
--- a/src/gravity/Default/gravity_part.h
+++ b/src/gravity/Default/gravity_part.h
@@ -50,6 +50,8 @@ struct gpart {
   /*! Type of the #gpart (DM, gas, star, ...) */
   enum part_type type;
 
+  size_t offset;
+
 #ifdef SWIFT_DEBUG_CHECKS
 
   /* Numer of gparts this gpart interacted with */
diff --git a/src/space.h b/src/space.h
index 76d9369db22740440831fe13eb4d57672e4f9951..23f01fedbffe9959a1338fa5bc90624c706226e6 100644
--- a/src/space.h
+++ b/src/space.h
@@ -155,6 +155,9 @@ struct space {
   /*! The associated engine. */
   struct engine *e;
 
+  /*! The FOF linking length squared. */
+  double l_x2;
+
 #ifdef WITH_MPI
 
   /*! Buffers for parts that we will receive from foreign cells. */