diff --git a/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh b/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh
index 0c949f9839e1..8d677affb9fe 100755
--- a/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh
+++ b/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh
@@ -209,11 +209,11 @@ function histo_check_test_pool
 	# 4096 blocksize count for asize.   For verification we stick
 	# to just lsize counts.
 	#
-	# The max_variance is hard-coded here at 10%.  testing so far
-	# has shown this to be in the range of 2%-8% so we leave a
-	# generous allowance... This might need changes in the future
+	# The max_variance is hard-coded here at 12% to leave us some
+	# margin.  Testing has shown this normally to be in the range
+	# of 2%-8%, but it may be as large as 11%.
 	###################
-	let max_variance=10
+	let max_variance=12
 	let fail_value=0
 	let error_count=0
 	log_note "Comparisons for ${pool}"