diff --git a/core/src/statusbar.sld b/core/src/statusbar.sld
index 492bf92..e2be98b 100644
--- a/core/src/statusbar.sld
+++ b/core/src/statusbar.sld
@@ -118,11 +118,12 @@
         (set! need-redraw #t))
 
       (define (bypass-write buf)
-        (mutex-lock! out-mutex)
-        (write-err-line buf 0 (bytevector-length buf))
-        (draw-status-bar)
-        (set! need-redraw #f)
-        (mutex-unlock! out-mutex))
+        (when (> (bytevector-length buf) 0)
+         (mutex-lock! out-mutex)
+         (write-err-line buf 0 (bytevector-length buf))
+         (draw-status-bar)
+         (set! need-redraw #f)
+         (mutex-unlock! out-mutex)))
        
       (define (close-this-port)
          (mutex-lock! out-mutex)
@@ -187,7 +188,7 @@
           (set! build-activity-mapping
             (mapping-set! build-activity-mapping (nix-activity-id data)
               (string-drop (string-drop-while (vector-ref (nix-activity-fields data) 0) (lambda (f) (not (char=? f #\-)))) 1))))
-         ((eqv? event 'activity-start) (set! statusbar-msg (nix-activity-string data)) (rerender-status-bar))
+         ((eqv? event 'activity-start) (when (> (string-length (nix-activity-string data)) 0) (set! statusbar-msg (nix-activity-string data)) (rerender-status-bar)))
          ((eqv? event 'activity-stop)
           (set! build-activity-mapping (mapping-delete! build-activity-mapping data)))
          ((and (eqv? event 'activity-result) (eqv? (nix-activity-type data) 101))