diff --git a/CHANGELOG.md b/CHANGELOG.md
index c33248e..45e2bb8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,8 @@
 # Yii Strings Change Log
 
-## 2.7.1 under development
+## 3.0.0 under development
 
+- Chg #165: Change default value of `$strict` parameter in `Inflector::toSnakeCase()` to `false` (@vjik)
 - New #156: Add `NumericHelper::trimDecimalZeros()` (@samdark, @vjik)
 - Enh #163: Explicitly import classes, functions, and constants in "use" sections (@vjik)
 
diff --git a/UPGRADE.md b/UPGRADE.md
index e7cb567..42dc833 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -7,7 +7,18 @@ application when you upgrade the package from one version to another.
 > to upgrade from version A to version C and there is version B between A and C, you need
 > to following the instructions for both A and B.
 
-## Upgrade from 1.2.0
+## Upgrade from 2.x to 3.x
+
+Default value of `$strict` parameter in `Inflector::toSnakeCase()` changed to `false`. To keep previous behaviour add 
+`strict: true` to call methods `Inflector::toSnakeCase()` without `strict` argument. For example:
+
+```php
+Inflector::toSnakeCase($name);
+// change to
+Inflector::toSnakeCase($name, true);
+```
+
+## Upgrade from 1.x to 2.x
 
 `\Yiisoft\Strings\WildCardPattern` was changed.
 
diff --git a/src/Inflector.php b/src/Inflector.php
index f9543be..289d468 100644
--- a/src/Inflector.php
+++ b/src/Inflector.php
@@ -613,11 +613,11 @@ public function toCamelCase(string $input): string
      * so "who's online" will be converted to "who_s_online".
      *
      * @param string $input The word to convert. It must be valid UTF-8 string.
-     * @param bool $strict Whether to insert a separator between two consecutive uppercase chars, defaults to true.
+     * @param bool $strict Whether to insert a separator between two consecutive uppercase chars, defaults to false.
      *
      * @return string The "snake_cased" string.
      */
-    public function toSnakeCase(string $input, bool $strict = true): string
+    public function toSnakeCase(string $input, bool $strict = false): string
     {
         /**
          * @var string $input We assume that `$input` is valid UTF-8 string, so `preg_replace()` never returns `false`.
diff --git a/tests/InflectorTest.php b/tests/InflectorTest.php
index 9b0cb8c..dbf87f7 100644
--- a/tests/InflectorTest.php
+++ b/tests/InflectorTest.php
@@ -130,13 +130,13 @@ public static function dataToSnakeCase(): array
     {
         return [
             [['input' => 'userName'], 'user_name'],
-            [['input' => 'travelSGuide'], 'travel_s_guide'],
+            [['input' => 'travelSGuide', 'strict' => true], 'travel_s_guide'],
             [['input' => 'ひらがなHepimiz'], 'ひらがな_hepimiz'],
             [['input' => 'Let\'s say "Hello, World!" yii 3 😂'], 'let_s_say_hello_world_yii_3'],
-            [['input' => 'HTML'], 'h_t_m_l'],
-            [['input' => 'createMyDTO'], 'create_my_d_t_o'],
-            [['input' => 'HTML', 'strict' => false], 'html'],
-            [['input' => 'createMyDTO', 'strict' => false], 'create_my_dto'],
+            [['input' => 'HTML', 'strict' => true], 'h_t_m_l'],
+            [['input' => 'createMyDTO', 'strict' => true], 'create_my_d_t_o'],
+            [['input' => 'HTML'], 'html'],
+            [['input' => 'createMyDTO'], 'create_my_dto'],
         ];
     }