diff --git a/td/telegram/InlineQueriesManager.cpp b/td/telegram/InlineQueriesManager.cpp
index c07a31ef..a3e9723c 100644
--- a/td/telegram/InlineQueriesManager.cpp
+++ b/td/telegram/InlineQueriesManager.cpp
@@ -330,7 +330,7 @@ void InlineQueriesManager::answer_inline_query(int64 inline_query_id, bool is_pe
     if (switch_pm_parameter.size() > 64) {
       return promise.set_error(Status::Error(400, "Too long switch_pm_parameter specified"));
     }
-    if (!is_base64url(switch_pm_parameter)) {
+    if (!is_base64url_characters(switch_pm_parameter)) {
       return promise.set_error(Status::Error(400, "Unallowed characters in switch_pm_parameter are used"));
     }
   }
diff --git a/tdutils/td/utils/base64.cpp b/tdutils/td/utils/base64.cpp
index e4ecb5e7..35d91690 100644
--- a/tdutils/td/utils/base64.cpp
+++ b/tdutils/td/utils/base64.cpp
@@ -216,6 +216,17 @@ Result<string> base64url_decode(Slice base64) {
   return output;
 }
 
+template <bool is_url>
+static const unsigned char *get_character_table() {
+  if (is_url) {
+    init_base64url_table();
+    return url_char_to_value;
+  } else {
+    init_base64_table();
+    return char_to_value;
+  }
+}
+
 template <bool is_url>
 static bool is_base64_impl(Slice input) {
   size_t padding_length = 0;
@@ -233,14 +244,7 @@ static bool is_base64_impl(Slice input) {
     return false;
   }
 
-  unsigned char *table;
-  if (is_url) {
-    init_base64url_table();
-    table = url_char_to_value;
-  } else {
-    init_base64_table();
-    table = char_to_value;
-  }
+  auto table = get_character_table<is_url>();
   for (auto c : input) {
     if (table[static_cast<unsigned char>(c)] == 64) {
       return false;
@@ -271,6 +275,25 @@ bool is_base64url(Slice input) {
   return is_base64_impl<true>(input);
 }
 
+template <bool is_url>
+static bool is_base64_characters_impl(Slice input) {
+  auto table = get_character_table<is_url>();
+  for (auto c : input) {
+    if (table[static_cast<unsigned char>(c)] == 64) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool is_base64_characters(Slice input) {
+  return is_base64_characters_impl<false>(input);
+}
+
+bool is_base64url_characters(Slice input) {
+  return is_base64_characters_impl<true>(input);
+}
+
 string base64_filter(Slice input) {
   string res;
   res.reserve(input.size());
diff --git a/tdutils/td/utils/base64.h b/tdutils/td/utils/base64.h
index 369c02a3..05ef1c7d 100644
--- a/tdutils/td/utils/base64.h
+++ b/tdutils/td/utils/base64.h
@@ -23,6 +23,9 @@ Result<string> base64url_decode(Slice base64);
 bool is_base64(Slice input);
 bool is_base64url(Slice input);
 
+bool is_base64_characters(Slice input);
+bool is_base64url_characters(Slice input);
+
 string base64_filter(Slice input);
 
 }  // namespace td
diff --git a/tdutils/test/misc.cpp b/tdutils/test/misc.cpp
index acda4e38..24953db1 100644
--- a/tdutils/test/misc.cpp
+++ b/tdutils/test/misc.cpp
@@ -183,6 +183,30 @@ TEST(Misc, base64) {
   ASSERT_TRUE(is_base64url("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/") == false);
   ASSERT_TRUE(is_base64url("====") == false);
 
+  ASSERT_TRUE(is_base64_characters("dGVzdA==") == false);
+  ASSERT_TRUE(is_base64_characters("dGVzdB==") == false);
+  ASSERT_TRUE(is_base64_characters("dGVzdA=") == false);
+  ASSERT_TRUE(is_base64_characters("dGVzdA") == true);
+  ASSERT_TRUE(is_base64_characters("dGVz") == true);
+  ASSERT_TRUE(is_base64_characters("") == true);
+  ASSERT_TRUE(is_base64_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/") == true);
+  ASSERT_TRUE(is_base64_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=") == false);
+  ASSERT_TRUE(is_base64_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-/") == false);
+  ASSERT_TRUE(is_base64_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_") == false);
+  ASSERT_TRUE(is_base64_characters("====") == false);
+
+  ASSERT_TRUE(is_base64url_characters("dGVzdA==") == false);
+  ASSERT_TRUE(is_base64url_characters("dGVzdB==") == false);
+  ASSERT_TRUE(is_base64url_characters("dGVzdA=") == false);
+  ASSERT_TRUE(is_base64url_characters("dGVzdA") == true);
+  ASSERT_TRUE(is_base64url_characters("dGVz") == true);
+  ASSERT_TRUE(is_base64url_characters("") == true);
+  ASSERT_TRUE(is_base64url_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_") == true);
+  ASSERT_TRUE(is_base64url_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_=") == false);
+  ASSERT_TRUE(is_base64url_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-/") == false);
+  ASSERT_TRUE(is_base64url_characters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/") == false);
+  ASSERT_TRUE(is_base64url_characters("====") == false);
+
   for (int l = 0; l < 300000; l += l / 20 + l / 1000 * 500 + 1) {
     for (int t = 0; t < 10; t++) {
       string s = rand_string(std::numeric_limits<char>::min(), std::numeric_limits<char>::max(), l);