diff --git a/Eventjet/ruleset.xml b/Eventjet/ruleset.xml
index 30d0245..d8607a3 100644
--- a/Eventjet/ruleset.xml
+++ b/Eventjet/ruleset.xml
@@ -92,6 +92,9 @@
     </rule>
     <rule ref="Generic.Strings.UnnecessaryStringConcat"/>
 
+    <!-- Avoid double quotes -->
+    <rule ref="Squiz.Strings.DoubleQuoteUsage"/>
+
     <!-- Forbid spaces in type casts -->
     <rule ref="Squiz.WhiteSpace.CastSpacing"/>
 
diff --git a/php-cs-fixer-rules.php b/php-cs-fixer-rules.php
index 395349a..e24bfaf 100644
--- a/php-cs-fixer-rules.php
+++ b/php-cs-fixer-rules.php
@@ -72,6 +72,7 @@
     ],
     'phpdoc_trim' => true,
     'php_unit_data_provider_static' => true,
+    'single_quote' => true,
     'single_space_around_construct' => true,
     'strict_comparison' => true,
     'trailing_comma_in_multiline' => [
diff --git a/tests/fixtures/invalid/double-quotes.php b/tests/fixtures/invalid/double-quotes.php
new file mode 100644
index 0000000..59430a6
--- /dev/null
+++ b/tests/fixtures/invalid/double-quotes.php
@@ -0,0 +1,5 @@
+<?php
+
+declare(strict_types=1);
+
+echo "double quotes";
diff --git a/tests/fixtures/valid/single-quotes.php b/tests/fixtures/valid/single-quotes.php
new file mode 100644
index 0000000..8ff1814
--- /dev/null
+++ b/tests/fixtures/valid/single-quotes.php
@@ -0,0 +1,5 @@
+<?php
+
+declare(strict_types=1);
+
+echo 'single quotes';