diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index 5526499b43..ea52acfbb8 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -494,7 +494,7 @@ virCommandMassCloseGetFDsDir(virBitmap *fds,
             return -1;
         }
 
-        ignore_value(virBitmapSetBit(fds, fd));
+        virBitmapSetBitExpand(fds, fd);
     }
 
     if (rc < 0)
@@ -539,9 +539,11 @@ virCommandMassCloseFrom(virCommand *cmd,
      * Therefore we can safely allocate memory here (and transitively call
      * opendir/readdir) without a deadlock. */
 
-    if (openmax < 0) {
-        virReportSystemError(errno, "%s", _("sysconf(_SC_OPEN_MAX) failed"));
-        return -1;
+    if (openmax <= 0) {
+        /* Darwin defaults to 10240. Start with a generous value.
+         * virCommandMassCloseGetFDsDir() uses virBitmapSetBitExpand() anyways.
+         */
+        openmax = 10240;
     }
 
     fds = virBitmapNew(openmax);