diff --git a/builtin-functions/kphp-full/kphp_toggles.txt b/builtin-functions/kphp-full/kphp_toggles.txt
index 5fd336e908..ca8f9024e9 100644
--- a/builtin-functions/kphp-full/kphp_toggles.txt
+++ b/builtin-functions/kphp-full/kphp_toggles.txt
@@ -4,8 +4,6 @@
 
 function set_migration_php8_warning ($mask ::: int) ::: void;
 
-function set_detect_incorrect_encoding_names_warning(bool $show) ::: void;
-
 function set_json_log_on_timeout_mode(bool $enabled) ::: void;
 
 function set_json_log_demangle_stacktrace(bool $enable) ::: void;
diff --git a/builtin-functions/kphp-light/kphp-toggles.txt b/builtin-functions/kphp-light/kphp-toggles.txt
index 1f5756057f..f4f5eb5ec5 100644
--- a/builtin-functions/kphp-light/kphp-toggles.txt
+++ b/builtin-functions/kphp-light/kphp-toggles.txt
@@ -1,7 +1,5 @@
 <?php
 
-function set_detect_incorrect_encoding_names_warning(bool $show) ::: void;
-
 /** @kphp-extern-func-info generate-stub */
 function kphp_turn_on_host_tag_in_inner_statshouse_metrics_toggle() ::: void;
 
diff --git a/runtime-common/stdlib/string/mbstring-functions.cpp b/runtime-common/stdlib/string/mbstring-functions.cpp
index cbe8887beb..1efe7c1caa 100644
--- a/runtime-common/stdlib/string/mbstring-functions.cpp
+++ b/runtime-common/stdlib/string/mbstring-functions.cpp
@@ -6,10 +6,9 @@
 
 #include "common/unicode/unicode-utils.h"
 #include "common/unicode/utf8-utils.h"
-#include "runtime-common/stdlib/string/string-context.h"
 #include "runtime-common/stdlib/string/string-functions.h"
 
-int mb_detect_encoding_new(const string &encoding) noexcept {
+int mb_detect_encoding(const string &encoding) noexcept {
   const auto *encoding_name = f$strtolower(encoding).c_str();
 
   if (!strcmp(encoding_name, "cp1251") || !strcmp(encoding_name, "cp-1251") || !strcmp(encoding_name, "windows-1251")) {
@@ -23,29 +22,6 @@ int mb_detect_encoding_new(const string &encoding) noexcept {
   return -1;
 }
 
-int mb_detect_encoding(const string &encoding) noexcept {
-  const int result_new = mb_detect_encoding_new(encoding);
-  const auto detect_incorrect_encoding_names = StringLibContext::get().detect_incorrect_encoding_names;
-
-  if (strstr(encoding.c_str(), "1251")) {
-    if (detect_incorrect_encoding_names && 1251 != result_new) {
-      php_warning("mb_detect_encoding returns 1251, but new will return %d, encoding %s", result_new, encoding.c_str());
-    }
-    return 1251;
-  }
-  if (strstr(encoding.c_str(), "-8")) {
-    if (detect_incorrect_encoding_names && 8 != result_new) {
-      php_warning("mb_detect_encoding returns 8, but new will return %d, encoding %s", result_new, encoding.c_str());
-    }
-    return 8;
-  }
-
-  if (detect_incorrect_encoding_names && -1 != result_new) {
-    php_warning("mb_detect_encoding returns -1, but new will return %d, encoding %s", result_new, encoding.c_str());
-  }
-  return -1;
-}
-
 int64_t mb_UTF8_strlen(const char *s) {
   int64_t res = 0;
   for (int64_t i = 0; s[i]; i++) {
diff --git a/runtime-common/stdlib/string/mbstring-functions.h b/runtime-common/stdlib/string/mbstring-functions.h
index 374422f8f7..cb0b0f77c0 100644
--- a/runtime-common/stdlib/string/mbstring-functions.h
+++ b/runtime-common/stdlib/string/mbstring-functions.h
@@ -27,11 +27,3 @@ Optional<int64_t> f$mb_stripos(const string &haystack, const string &needle, int
 
 string f$mb_substr(const string &str, int64_t start, const mixed &length = std::numeric_limits<int64_t>::max(),
                    const string &encoding = StringLibConstants::get().CP1251_STR) noexcept;
-
-inline void f$set_detect_incorrect_encoding_names_warning(bool show) noexcept {
-  StringLibContext::get().detect_incorrect_encoding_names = show;
-}
-
-inline void free_detect_incorrect_encoding_names() noexcept {
-  StringLibContext::get().detect_incorrect_encoding_names = false;
-}
diff --git a/runtime-common/stdlib/string/string-context.h b/runtime-common/stdlib/string/string-context.h
index d655fc18fe..af2809ebf1 100644
--- a/runtime-common/stdlib/string/string-context.h
+++ b/runtime-common/stdlib/string/string-context.h
@@ -42,9 +42,6 @@ class StringLibContext final : vk::not_copyable {
   int64_t str_replace_count_dummy{};
   double default_similar_text_percent_stub{};
 
-  // mb_string context
-  bool detect_incorrect_encoding_names{};
-
   static StringLibContext &get() noexcept;
 };
 
diff --git a/runtime/interface.cpp b/runtime/interface.cpp
index ce9a1573c9..bbc7042c2c 100644
--- a/runtime/interface.cpp
+++ b/runtime/interface.cpp
@@ -2388,7 +2388,6 @@ static void free_runtime_libs() {
   free_kphp_backtrace();
 
   free_use_updated_gmmktime();
-  free_detect_incorrect_encoding_names();
 
   vk::singleton<JsonLogger>::get().reset_buffers();
 #ifdef PDO_DRIVER_MYSQL