diff --git a/components/script/dom/textencoder.rs b/components/script/dom/textencoder.rs
index 91a02257d71..03c4902ec11 100644
--- a/components/script/dom/textencoder.rs
+++ b/components/script/dom/textencoder.rs
@@ -14,7 +14,6 @@ use dom::bindings::utils::{Reflector, reflect_dom_object};
 use util::str::DOMString;
 
 use std::borrow::ToOwned;
-use std::ascii::AsciiExt;
 use std::ptr;
 
 use encoding::types::EncodingRef;
@@ -50,7 +49,7 @@ impl TextEncoder {
     // https://encoding.spec.whatwg.org/#dom-textencoder
     pub fn Constructor(global: GlobalRef,
                        label: DOMString) -> Fallible<Temporary<TextEncoder>> {
-        let encoding = match encoding_from_whatwg_label(&label.trim().to_ascii_lowercase()) {
+        let encoding = match encoding_from_whatwg_label(&label) {
             Some(enc) => enc,
             None => {
                 debug!("Encoding Label Not Supported");
diff --git a/tests/wpt/metadata/encoding/api-invalid-label.html.ini b/tests/wpt/metadata/encoding/api-invalid-label.html.ini
deleted file mode 100644
index 3f31413c569..00000000000
--- a/tests/wpt/metadata/encoding/api-invalid-label.html.ini
+++ /dev/null
@@ -1,218 +0,0 @@
-[api-invalid-label.html]
-  type: testharness
-  [Invalid label "\\vunicode-1-1-utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "unicode-1-1-utf-8\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vunicode-1-1-utf-8\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " unicode-1-1-utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "unicode-1-1-utf-8 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " unicode-1-1-utf-8 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
unicode-1-1-utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "unicode-1-1-utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
unicode-1-1-utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
unicode-1-1-utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "unicode-1-1-utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
unicode-1-1-utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-8\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-8\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-8 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-8 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf8\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf8\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf8 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf8 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf8" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf8
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-16be" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16be\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-16be\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-16be" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16be " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-16be " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16be" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16be
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16be
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16be" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16be
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16be
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-16" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-16\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-16" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-16 " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-16le" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16le\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "\\vutf-16le\\v" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-16le" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16le " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label " utf-16le " should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16le" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16le
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16le
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16le" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "utf-16le
" should be rejected by TextEncoder.]
-    expected: FAIL
-
-  [Invalid label "
utf-16le
" should be rejected by TextEncoder.]
-    expected: FAIL
-