diff --git a/src/cell.h b/src/cell.h
index b8cb6054fcdefbb5b338b513ef664c404675fccf..107c41d9cb9d9229f58be9fb176a62f0db829de3 100644
--- a/src/cell.h
+++ b/src/cell.h
@@ -27,9 +27,6 @@
 /* Forward declaration of space, needed for cell_unpack. */
 struct space;
 
-/* Some constants. */
-#define cell_sid_dt 13
-
 /* Max tag size set to 2^29 to take into account some MPI implementations 
  * that use 2^31 as the upper bound on MPI tags and the fact that 
  * cell_next_tag is multiplied by 2 when passed to an MPI function. 
diff --git a/src/space.h b/src/space.h
index 6387b9feee527c6f290f3ca75d36ac34d4f982e7..91d3d9a4d34aefcdcc52e774e6feb492577275b6 100644
--- a/src/space.h
+++ b/src/space.h
@@ -29,13 +29,11 @@ struct engine;
 /* Some constants. */
 #define space_maxdepth 10
 #define space_cellallocchunk 1000
-#define space_splitratio 0.875f
 #define space_splitsize_default 400
 #define space_maxsize_default 8000000
 #define space_subsize_default 8000000
 #define space_stretch 1.10f
 #define space_maxreldx 0.25f
-#define space_qstack 2048
 
 /* Split size. */
 extern int space_splitsize;