diff --git a/ktor-http/common/src/io/ktor/http/auth/HttpAuthHeader.kt b/ktor-http/common/src/io/ktor/http/auth/HttpAuthHeader.kt
index 47cbf25b625..0fa08090d5a 100644
--- a/ktor-http/common/src/io/ktor/http/auth/HttpAuthHeader.kt
+++ b/ktor-http/common/src/io/ktor/http/auth/HttpAuthHeader.kt
@@ -61,6 +61,7 @@ public fun parseAuthorizationHeader(headerValue: String): HttpAuthHeader? {
  * @return a list of [HttpAuthHeader]
  * @throws [ParseException] on invalid header
  */
+@InternalAPI
 public fun parseAuthorizationHeaders(headerValue: String): List<HttpAuthHeader> {
     var index = 0
     val headers = mutableListOf<HttpAuthHeader>()
@@ -107,6 +108,12 @@ private fun parseAuthorizationHeader(
     return nextIndexChallenge
 }
 
+/**
+ * Check for the ending of the current challenge in a header
+ * @return -1 if at the end of the header
+ * @return null if the challenge is not ended
+ * @return a positive number - the index of the beginning of the next challenge
+ */
 private fun nextChallengeIndex(
     headers: MutableList<HttpAuthHeader>,
     header: HttpAuthHeader,
diff --git a/ktor-server/ktor-server-plugins/ktor-server-auth/jvmAndNix/test/io/ktor/tests/auth/AuthorizeHeaderParserTest.kt b/ktor-server/ktor-server-plugins/ktor-server-auth/jvmAndNix/test/io/ktor/tests/auth/AuthorizeHeaderParserTest.kt
index 0519f3dd0fc..2179514e38b 100644
--- a/ktor-server/ktor-server-plugins/ktor-server-auth/jvmAndNix/test/io/ktor/tests/auth/AuthorizeHeaderParserTest.kt
+++ b/ktor-server/ktor-server-plugins/ktor-server-auth/jvmAndNix/test/io/ktor/tests/auth/AuthorizeHeaderParserTest.kt
@@ -5,6 +5,7 @@
 package io.ktor.tests.auth
 
 import io.ktor.http.auth.*
+import io.ktor.util.*
 import kotlin.random.*
 import kotlin.test.*
 
@@ -114,6 +115,7 @@ class AuthorizeHeaderParserTest {
         }
     }
 
+    @OptIn(InternalAPI::class)
     private fun testParserMultipleChallenges(expected: List<HttpAuthHeader>, headerValue: String) {
         val actual = parseAuthorizationHeaders(headerValue)