diff --git a/src/llhttp/constants.ts b/src/llhttp/constants.ts
index bdf8afbe..00fc5239 100644
--- a/src/llhttp/constants.ts
+++ b/src/llhttp/constants.ts
@@ -504,6 +504,17 @@ for (let i = 0x21; i <= 0xff; i++) {
   }
 }
 
+export const HTAB_SP_VCHAR_OBS_TEXT: CharList = [ '\t', ' ' ];
+
+// VCHAR: https://tools.ietf.org/html/rfc5234#appendix-B.1
+for (let i = 0x21; i <= 0x7E; i++) {
+    HTAB_SP_VCHAR_OBS_TEXT.push(i);
+}
+// OBS_TEXT: https://datatracker.ietf.org/doc/html/rfc9110#name-collected-abnf
+for (let i = 0x80; i <= 0xff; i++) {
+    HTAB_SP_VCHAR_OBS_TEXT.push(i);
+}
+
 export const MAJOR = NUM_MAP;
 export const MINOR = MAJOR;
 
diff --git a/src/llhttp/http.ts b/src/llhttp/http.ts
index 71a7c422..d0bfd480 100644
--- a/src/llhttp/http.ts
+++ b/src/llhttp/http.ts
@@ -7,7 +7,7 @@ import Node = source.node.Node;
 import {
   CharList,
   CONNECTION_TOKEN_CHARS, ERROR, FINISH, FLAGS, H_METHOD_MAP, HEADER_CHARS,
-  HEADER_STATE, HEX_MAP,
+  HEADER_STATE, HEX_MAP, HTAB_SP_VCHAR_OBS_TEXT,
   LENIENT_FLAGS,
   MAJOR, METHOD_MAP, METHODS, METHODS_HTTP, METHODS_ICE, METHODS_RTSP,
   MINOR, NUM_MAP, QUOTED_STRING, SPECIAL_HEADERS,
@@ -94,6 +94,7 @@ const NODES: ReadonlyArray<string> = [
   'chunk_extension_name',
   'chunk_extension_value',
   'chunk_extension_quoted_value',
+  'chunk_extension_quoted_value_quoted_pair',
   'chunk_extension_quoted_value_done',
   'chunk_data',
   'chunk_data_almost_done',
@@ -989,10 +990,17 @@ export class HTTP {
       .match('"', this.span.chunkExtensionValue.end(
         onChunkExtensionValueCompleted(n('chunk_extension_quoted_value_done')),
       ))
+      .match('\\', n('chunk_extension_quoted_value_quoted_pair'))
       .otherwise(this.span.chunkExtensionValue.end().skipTo(
         p.error(ERROR.STRICT, 'Invalid character in chunk extensions quoted value'),
       ));
 
+    n('chunk_extension_quoted_value_quoted_pair')
+      .match(HTAB_SP_VCHAR_OBS_TEXT, n('chunk_extension_quoted_value'))
+      .otherwise(this.span.chunkExtensionValue.end().skipTo(
+        p.error(ERROR.STRICT, 'Invalid quoted-pair in chunk extensions quoted value'),
+      ));
+
     n('chunk_extension_quoted_value_done')
       .match(';', n('chunk_extensions'))
       .match('\r', n('chunk_size_almost_done'))
diff --git a/test/request/transfer-encoding.md b/test/request/transfer-encoding.md
index 69e8cf9a..0f839bcc 100644
--- a/test/request/transfer-encoding.md
+++ b/test/request/transfer-encoding.md
@@ -352,7 +352,7 @@ off=98 error code=2 reason="Invalid character in chunk extensions"
 POST /chunked_w_unicorns_after_length HTTP/1.1
 Transfer-Encoding: chunked
 
-5;ilovew3="I love; extensions";somuchlove="aretheseparametersfor";blah;foo=bar
+5;ilovew3="I \"love\"; \\extensions\\";somuchlove="aretheseparametersfor";blah;foo=bar
 hello
 6;blahblah;blah
  world
@@ -375,29 +375,29 @@ off=76 header_value complete
 off=78 headers complete method=3 v=1/1 flags=208 content_length=0
 off=80 len=7 span[chunk_extension_name]="ilovew3"
 off=88 chunk_extension_name complete
-off=88 len=20 span[chunk_extension_value]=""I love; extensions""
-off=108 chunk_extension_value complete
-off=109 len=10 span[chunk_extension_name]="somuchlove"
-off=120 chunk_extension_name complete
-off=120 len=23 span[chunk_extension_value]=""aretheseparametersfor""
-off=143 chunk_extension_value complete
-off=144 len=4 span[chunk_extension_name]="blah"
-off=149 chunk_extension_name complete
-off=149 len=3 span[chunk_extension_name]="foo"
-off=153 chunk_extension_name complete
-off=153 len=3 span[chunk_extension_value]="bar"
-off=157 chunk_extension_value complete
-off=158 chunk header len=5
-off=158 len=5 span[body]="hello"
-off=165 chunk complete
-off=167 len=8 span[chunk_extension_name]="blahblah"
-off=176 chunk_extension_name complete
-off=176 len=4 span[chunk_extension_name]="blah"
-off=181 chunk_extension_name complete
-off=182 chunk header len=6
-off=182 len=6 span[body]=" world"
-off=190 chunk complete
-off=193 chunk header len=0
+off=88 len=28 span[chunk_extension_value]=""I \"love\"; \\extensions\\""
+off=116 chunk_extension_value complete
+off=117 len=10 span[chunk_extension_name]="somuchlove"
+off=128 chunk_extension_name complete
+off=128 len=23 span[chunk_extension_value]=""aretheseparametersfor""
+off=151 chunk_extension_value complete
+off=152 len=4 span[chunk_extension_name]="blah"
+off=157 chunk_extension_name complete
+off=157 len=3 span[chunk_extension_name]="foo"
+off=161 chunk_extension_name complete
+off=161 len=3 span[chunk_extension_value]="bar"
+off=165 chunk_extension_value complete
+off=166 chunk header len=5
+off=166 len=5 span[body]="hello"
+off=173 chunk complete
+off=175 len=8 span[chunk_extension_name]="blahblah"
+off=184 chunk_extension_name complete
+off=184 len=4 span[chunk_extension_name]="blah"
+off=189 chunk_extension_name complete
+off=190 chunk header len=6
+off=190 len=6 span[body]=" world"
+off=198 chunk complete
+off=201 chunk header len=0
 ```