diff --git a/src/main/java/org/swisspush/redisques/performance/UpperBoundParallel.java b/src/main/java/org/swisspush/redisques/performance/UpperBoundParallel.java
index b5baf62..6913213 100644
--- a/src/main/java/org/swisspush/redisques/performance/UpperBoundParallel.java
+++ b/src/main/java/org/swisspush/redisques/performance/UpperBoundParallel.java
@@ -135,7 +135,9 @@ private <Ctx> void onOneDone(Request<Ctx> req, Throwable ex) {
                 // Unlock, to prevent thread stalls as we don't know for how long mentor
                 // is going to block.
                 req.lock.unlock();
-                log.debug("mentor.onError({}: {})", ex.getClass().getName(), ex.getMessage());
+                if (log.isDebugEnabled()) {
+                    log.debug("mentor.onError({}: {})", ex.getClass().getName(), ex.getMessage());
+                }
                 isFatalError = req.mentor.onError(ex, req.ctx);
             } finally {
                 req.lock.lock(); // Need our lock back.