diff --git a/tcl/drivers/ccu4flow.tcl b/tcl/drivers/ccu4flow.tcl
index 56c32ea..1f43872 100644
--- a/tcl/drivers/ccu4flow.tcl
+++ b/tcl/drivers/ccu4flow.tcl
@@ -405,7 +405,7 @@ proc ccu4flow::ctrl {} {
         set regstate 0
       }
     } else {
-      if {[silent 0 sct release_blocked]} {
+      if {[silent 0 sct release_blocked] && $ist > $soll + $tol} {
         # hack for releasing n.v. at MA7
         setstate closed
         set closecnt [silent 1 sct closecnt]