diff --git a/src/engine.c b/src/engine.c
index d962105578c01f5bb9abf0c5f7c31c59ae22eda4..e285c74635beb5b807082a1be4f2ff2efdec845c 100644
--- a/src/engine.c
+++ b/src/engine.c
@@ -1644,14 +1644,14 @@ void engine_makeproxies(struct engine *e) {
 #ifdef WITH_MPI
   const int *cdim = e->s->cdim;
   const struct space *s = e->s;
-  const struct cell *cells = s->cells;
+  struct cell *cells = s->cells;
   struct proxy *proxies = e->proxies;
 
   /* Prepare the proxies and the proxy index. */
   if (e->proxy_ind == NULL)
     if ((e->proxy_ind = (int *)malloc(sizeof(int) * e->nr_nodes)) == NULL)
       error("Failed to allocate proxy index.");
-  for (k = 0; k < e->nr_nodes; k++) e->proxy_ind[k] = -1;
+  for (int k = 0; k < e->nr_nodes; k++) e->proxy_ind[k] = -1;
   e->nr_proxies = 0;
 
   /* The following loop is super-clunky, but it's necessary