diff --git a/libcorpus2/tagset.cpp b/libcorpus2/tagset.cpp
index fd0af7be58fdbee633ce8344cfc3a3ad4655b62a..8ae89fe8ce636626ab3651e2670429508580a815 100644
--- a/libcorpus2/tagset.cpp
+++ b/libcorpus2/tagset.cpp
@@ -609,7 +609,7 @@ Tag Tagset::expand_unspec_attrs(const Tag& tag) const
 	Tag new_tag(tag);
 	idx_t pos_idx = tag.get_pos_index();
 	const std::vector<idx_t>& attrs = get_pos_attributes(pos_idx);
-	foreach (const idx_t& a, attrs) {
+	for (idx_t a = 0; a < attribute_count(); ++a) {
 		mask_t attr_mask = get_attribute_mask(a);
 		mask_t value = tag.get_values_for(attr_mask);
 		if (!value.any()) { // no value given
diff --git a/libcorpus2/tagset.h b/libcorpus2/tagset.h
index 271a7353fd2dbe2478fde435a52321463d662547..504dc22343da59260d43996edce3a9874041cd14 100644
--- a/libcorpus2/tagset.h
+++ b/libcorpus2/tagset.h
@@ -374,12 +374,12 @@ public:
 	Tag select_singular(const Tag& tag) const;
 
 	/**
-	  * Creates a copy of the given tag where optional or required attributes
-	  * with no value given are encoded as each possible value set.
-	  * NOTE: this may result in tags technically invalid (multiple values set
-	  * for one attribute), yet it is convenient for some tagging scenarios to
-	  * explicitly distinguish between an irrelevant attribute and a relevant
-	  * one but no value given.
+	  * Creates a copy of the given tag where any attribute with no value given
+	  * is encoded as each possible value set. NOTE: this produce an invalid
+	  * tag (multiple values set for one attribute), yet it is convenient for
+	  * some tagging scenarios to be able to retrieve unspecified attr value as
+	  * a non-zero mask. This can always be decoded into a valid tag by using
+	  * select_singular.
 	  */
 	Tag expand_unspec_attrs(const Tag& tag) const;