diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 2538c6a..75a8581 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -87,7 +87,7 @@ jobs:
 
     - name: Check code style
       if: matrix.php-versions == env.code-coverage-version
-      run: composer run-script phpcs -- --report=checkstyle | cs2pr
+      run: composer run-script phpcs -- --report=checkstyle | cs2pr --graceful-warnings
 
     - name: Run PHPUnit tests
       if: matrix.php-versions != env.code-coverage-version
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index cad2f55..931fd08 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -25,7 +25,6 @@
     <rule ref="SlevomatCodingStandard.Functions.UselessParameterDefaultValue"/>
     <rule ref="SlevomatCodingStandard.Namespaces.AlphabeticallySortedUses"/>
     <rule ref="SlevomatCodingStandard.Namespaces.UnusedUses"/>
-    <rule ref="SlevomatCodingStandard.Namespaces.UnusedUses"/>
     <rule ref="SlevomatCodingStandard.TypeHints.ParameterTypeHint"/>
     <rule ref="SlevomatCodingStandard.TypeHints.PropertyTypeHint"/>
     <rule ref="SlevomatCodingStandard.TypeHints.ReturnTypeHint"/>
diff --git a/src/Serializer.php b/src/Serializer.php
index de7d9d5..4fe9b6b 100644
--- a/src/Serializer.php
+++ b/src/Serializer.php
@@ -178,7 +178,7 @@ private static function serializeBoolean(bool $value): string
 
     private static function serializeInteger(int $value): string
     {
-        if ($value > 999999999999999 || $value < -999999999999999) {
+        if ($value > 999_999_999_999_999 || $value < -999_999_999_999_999) {
             throw new SerializeException("Integers are limited to 15 digits");
         }
         return (string) $value;
@@ -186,14 +186,16 @@ private static function serializeInteger(int $value): string
 
     private static function serializeDecimal(float $value): string
     {
-        if (abs(floor($value)) > 999999999999) {
-            throw new SerializeException("Integer portion of decimals is limited to 12 digits");
+        $value = round($value, 3, PHP_ROUND_HALF_EVEN);
+
+        if (abs(floor($value)) > 999_999_999_999) {
+            throw new SerializeException("Integer portion of decimals is limited to 12 digits after rounding to three decimal places");
         }
 
         // Casting to a string loses a digit on long numbers, but is preserved
-        // by json_encode (e.g. 111111111111.111).
+        // by json_encode (e.g. 111_111_111_111.111).
         /** @var non-empty-string $result */
-        $result = json_encode(round($value, 3, PHP_ROUND_HALF_EVEN));
+        $result = json_encode($value);
 
         if (!str_contains($result, '.')) {
             $result .= '.0';