diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 666b9ab96c..389eaace72 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -745,7 +745,7 @@ static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, uint64_t start,
     assert(bmap_start % BITS_PER_LONG == 0);
     /* We should never do log_clear before log_sync */
     assert(mem->dirty_bmap);
-    if (start_delta) {
+    if (start_delta || bmap_npages - size / psize) {
         /* Slow path - we need to manipulate a temp bitmap */
         bmap_clear = bitmap_new(bmap_npages);
         bitmap_copy_with_src_offset(bmap_clear, mem->dirty_bmap,
@@ -758,7 +758,10 @@ static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, uint64_t start,
         bitmap_clear(bmap_clear, 0, start_delta);
         d.dirty_bitmap = bmap_clear;
     } else {
-        /* Fast path - start address aligns well with BITS_PER_LONG */
+        /*
+         * Fast path - both start and size align well with BITS_PER_LONG
+         * (or the end of memory slot)
+         */
         d.dirty_bitmap = mem->dirty_bmap + BIT_WORD(bmap_start);
     }