diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index c6659cb370331fa8afed30ee366b9b2432b9c6f0..59875eb278ea55f2683955dae36f7ebcbdc43bcd 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -768,9 +768,11 @@ static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
 		new_s0->index_key[i] =
 			ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
 
-	blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
-	pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
-	new_s0->index_key[keylen - 1] &= ~blank;
+	if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) {
+		blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
+		pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
+		new_s0->index_key[keylen - 1] &= ~blank;
+	}
 
 	/* This now reduces to a node splitting exercise for which we'll need
 	 * to regenerate the disparity table.