diff --git a/libguile/posix.c b/libguile/posix.c
index bebf523dc..f514f168f 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -584,7 +584,7 @@ SCM
 scm_getpgrp ()
 {
   int (*fn)();
-  fn = getpgrp;
+  fn = (int (*) ()) getpgrp;
   return SCM_MAKINUM (fn (0));
 }