diff --git a/src/libslic3r/GCode/ConflictChecker.cpp b/src/libslic3r/GCode/ConflictChecker.cpp
index acf6b71f0..1c0c7f3d8 100644
--- a/src/libslic3r/GCode/ConflictChecker.cpp
+++ b/src/libslic3r/GCode/ConflictChecker.cpp
@@ -122,7 +122,9 @@ float LinesBucketQueue::getCurrBottomZ()
     }
 
     for (LinesBucket *bp : lowests) {
+        float prevZ = bp->curBottomZ();
         bp->raise();
+        if (bp->curBottomZ() == prevZ) continue;
         if (bp->valid()) { line_bucket_ptr_queue.push(bp); }
     }
     return layerBottomZ;