diff --git a/src/engine.c b/src/engine.c
index b4447d281e19c688bf0a8c6dfb191ec4c069393e..d98a0535632b801d2d6b715aebd270e4fc483c51 100644
--- a/src/engine.c
+++ b/src/engine.c
@@ -32,7 +32,7 @@
 #include <stdbool.h>
 
 /* MPI headers. */
-#if 1  //#ifdef WITH_MPI
+#ifdef WITH_MPI
 #include <mpi.h>
 #endif