diff --git a/module/os/windows/zfs/zfs_vnops_windows.c b/module/os/windows/zfs/zfs_vnops_windows.c
index 2394031d9eb2..24f435940a50 100644
--- a/module/os/windows/zfs/zfs_vnops_windows.c
+++ b/module/os/windows/zfs/zfs_vnops_windows.c
@@ -5026,7 +5026,7 @@ zfs_write_wrap(PDEVICE_OBJECT DeviceObject, PIRP Irp,
 		    (uint64_t)vp->FileHeader.AllocationSize.QuadPart) {
 
 			Status = zfs_freesp(zp,
-			    newlength, 0, FWRITE, B_TRUE);
+			    newlength, 0, FWRITE, B_FALSE);
 			if (!NT_SUCCESS(Status)) {
 				dprintf("extend_file returned %08lx\n",
 				    Status);
diff --git a/module/os/windows/zfs/zfs_znode.c b/module/os/windows/zfs/zfs_znode.c
index eff94188fffb..bfa2e41b3bc3 100644
--- a/module/os/windows/zfs/zfs_znode.c
+++ b/module/os/windows/zfs/zfs_znode.c
@@ -550,6 +550,9 @@ zfs_znode_alloc(zfsvfs_t *zfsvfs, dmu_buf_t *db, int blksz,
 	ASSERT(zp->z_dirlocks == NULL);
 	ASSERT(!POINTER_IS_VALID(zp->z_zfsvfs));
 
+	if (blksz == 0)
+		blksz = 0x200;
+
 	/*
 	 * Defer setting z_zfsvfs until the znode is ready to be a candidate for
 	 * the zfs_znode_move() callback.
diff --git a/module/zfs/zfs_log.c b/module/zfs/zfs_log.c
index ee973d40f701..613fcdb2327a 100644
--- a/module/zfs/zfs_log.c
+++ b/module/zfs/zfs_log.c
@@ -676,6 +676,8 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 		else if (wr_state == WR_INDIRECT)
 			len = MIN(blocksize - P2PHASE(off, blocksize), resid);
 
+		ASSERT3U(len, >, 0);
+
 		itx = zil_itx_create(txtype, sizeof (*lr) +
 		    (wr_state == WR_COPIED ? len : 0));
 		lr = (lr_write_t *)&itx->itx_lr;