diff --git a/libguile/posix.c b/libguile/posix.c
index 9a873b5a1..0e57f012b 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -282,7 +282,7 @@ SCM_DEFINE (scm_pipe2, "pipe", 0, 1, 0,
     /* 'pipe2' cannot be emulated on systems that lack it: calling
        'fnctl' afterwards to set the relevant flags is not equivalent
        because it's not atomic.  */
-    rv = ENOSYS;
+    rv = -1, errno = ENOSYS;
 #endif
 
   if (rv)