diff --git a/src/engine/execunix.c b/src/engine/execunix.c
index 0eb03ca3a..2b297a341 100644
--- a/src/engine/execunix.c
+++ b/src/engine/execunix.c
@@ -9,6 +9,12 @@
 # include "execcmd.h"
 # include <errno.h>
 
+
+#if defined(sun) || defined(__sun)
+#include <unistd.h> // need to include unistd.h on sun for the vfork prototype
+#include <wait.h>
+#endif
+
 # ifdef USE_EXECUNIX
 
 # ifdef NO_VFORK