diff --git a/src/attrs.c b/src/attrs.c
index 4f1c449..bfdca57 100644
--- a/src/attrs.c
+++ b/src/attrs.c
@@ -824,15 +824,15 @@ static const Attribute* attrsLookup(TidyDocImpl* doc,
 
 #if ATTRIBUTE_HASH_LOOKUP
     for (p = attribs->hashtab[attrsHash(atnam)]; p && p->attr; p = p->next)
-        if (TY_(tmbstrcmp)(atnam, p->attr->name) == 0)
+        if (TY_(tmbstrcasecmp)(atnam, p->attr->name) == 0)
             return p->attr;
 
     for (np = attribute_defs; np && np->name; ++np)
-        if (TY_(tmbstrcmp)(atnam, np->name) == 0)
+        if (TY_(tmbstrcasecmp)(atnam, np->name) == 0)
             return attrsInstall(doc, attribs, np);
 #else
     for (np = attribute_defs; np && np->name; ++np)
-        if (TY_(tmbstrcmp)(atnam, np->name) == 0)
+        if (TY_(tmbstrcasecmp)(atnam, np->name) == 0)
             return np;
 #endif