diff --git a/src/main/c/stream/helper/tagname.c b/src/main/c/stream/helper/tagname.c
index eb86392..9edce60 100644
--- a/src/main/c/stream/helper/tagname.c
+++ b/src/main/c/stream/helper/tagname.c
@@ -2,12 +2,15 @@
 #define _HDR_HYPERBUILD_STREAM_HELPER_TAGNAME
 
 #include "../../rule/char/tagname.c"
+#include "../../rule/char/ucalpha.c"
 
 #include "../../util/hbchar.h"
 #include "../../util/buffer.c"
 #include "../../util/pipe.c"
 
-hbu_buffer_t hbsh_tagname(hbu_pipe_t pipe) {
+#include "../streamoptions.c"
+
+hbu_buffer_t hbsh_tagname(hbs_options_t so, hbu_pipe_t pipe) {
   hbu_buffer_t name = hbu_buffer_create();
 
   while (1) {
@@ -17,11 +20,23 @@ hbu_buffer_t hbsh_tagname(hbu_pipe_t pipe) {
       break;
     }
 
-    hbu_buffer_append(name, c);
+    if (hbr_ucalpha_check(c)) {
+      if (!hbs_options_supressed_error(so, HBE_PARSE_UCASE_TAG)) {
+        hbu_pipe_error(pipe, HBE_PARSE_UCASE_TAG, "Uppercase character in tag");
+      }
+      // Lowercase to normalise when checking against rules and closing tag
+      hbu_buffer_append(name, c + 32);
+    } else {
+      hbu_buffer_append(name, c);
+    }
 
     hbu_pipe_accept(pipe);
   }
 
+  if (!hbs_options_supressed_error(so, HBE_PARSE_NONSTANDARD_TAG) && !hbr_tags_check(hbu_buffer_underlying(name))) {
+    hbu_pipe_error(pipe, HBE_PARSE_NONSTANDARD_TAG, "Non-standard tag");
+  }
+
   return name;
 }
 
diff --git a/src/main/c/stream/tag.c b/src/main/c/stream/tag.c
index 508de72..c136da4 100644
--- a/src/main/c/stream/tag.c
+++ b/src/main/c/stream/tag.c
@@ -24,7 +24,7 @@ void hbs_tag(hbs_options_t so, hbu_pipe_t pipe) {
   int self_closing = 0;
 
   hbu_pipe_require(pipe, '<');
-  hbu_buffer_t opening_name = hbsh_tagname(pipe);
+  hbu_buffer_t opening_name = hbsh_tagname(so, pipe);
   while (1) {
     hbu_pipe_accept_while_predicate(pipe, &hbr_whitespace_check);
 
@@ -49,9 +49,7 @@ void hbs_tag(hbs_options_t so, hbu_pipe_t pipe) {
 
   hb_char_t *tag_name = hbu_buffer_underlying(opening_name);
 
-  if (!hbs_options_supressed_error(so, HBE_PARSE_NONSTANDARD_TAG) && !hbr_tags_check(tag_name)) {
-    hbu_pipe_error(pipe, HBE_PARSE_NONSTANDARD_TAG, "Non-standard tag");
-  }
+  // Non-standard tag checking is done in hbsh_tagname
 
   // Self-closing or void tag
   if (self_closing || hbr_voidtags_check(tag_name)) {
@@ -72,7 +70,7 @@ void hbs_tag(hbs_options_t so, hbu_pipe_t pipe) {
   // Closing tag for non-void
   hbu_pipe_require(pipe, '<');
   hbu_pipe_require(pipe, '/');
-  hbu_buffer_t closing_name = hbsh_tagname(pipe);
+  hbu_buffer_t closing_name = hbsh_tagname(so, pipe);
   hbu_pipe_require(pipe, '>');
 
   if (!hbu_buffer_equal(opening_name, closing_name)) {