diff --git a/src/john-mpi.c b/src/john-mpi.c
index 9b9ba85..1e7fc4d 100644
--- a/src/john-mpi.c
+++ b/src/john-mpi.c
@@ -3,7 +3,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 int mpi_p, mpi_id, namesize;
 char mpi_name[MPI_MAX_PROCESSOR_NAME + 1];