diff --git a/src/engine.c b/src/engine.c
index 09028a52c0ff7b6a18ec9c41f73465476daf869a..4e73118dea7f6a4ec8f98a24001c292fa4d61fff 100644
--- a/src/engine.c
+++ b/src/engine.c
@@ -557,7 +557,7 @@ void engine_repartition(struct engine *e) {
     /* Check that the nodeIDs are ok. */
     for (k = 0; k < nr_cells; k++)
       if (nodeIDs[k] < 0 || nodeIDs[k] >= nr_nodes)
-        error("Got bad nodeID %i for cell %i.", nodeIDs[k], k);
+        error("Got bad nodeID %"PRIDX" for cell %i.", nodeIDs[k], k);
   }
 
 /* Broadcast the result of the partition. */