diff --git a/lib/AbstractPicoPlugin.php b/lib/AbstractPicoPlugin.php
index 68587f0..2b7a56c 100644
--- a/lib/AbstractPicoPlugin.php
+++ b/lib/AbstractPicoPlugin.php
@@ -199,7 +199,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
             }
 
             // plugins which don't implement PicoPluginInterface are always enabled
-            if (is_a($plugin, 'PicoPluginInterface') && !$plugin->isEnabled()) {
+            if (($plugin instanceof PicoPluginInterface) && !$plugin->isEnabled()) {
                 if ($recursive) {
                     if (!$plugin->isStatusChanged()) {
                         $plugin->setEnabled(true, true, true);
@@ -272,7 +272,7 @@ abstract class AbstractPicoPlugin implements PicoPluginInterface
             $this->dependants = array();
             foreach ($this->getPlugins() as $pluginName => $plugin) {
                 // only plugins which implement PicoPluginInterface support dependencies
-                if (is_a($plugin, 'PicoPluginInterface')) {
+                if ($plugin instanceof PicoPluginInterface) {
                     $dependencies = $plugin->getDependencies();
                     if (in_array(get_called_class(), $dependencies)) {
                         $this->dependants[$pluginName] = $plugin;
diff --git a/lib/Pico.php b/lib/Pico.php
index 12bd993..eada6de 100644
--- a/lib/Pico.php
+++ b/lib/Pico.php
@@ -457,7 +457,7 @@ class Pico
         }
 
         $className = get_class($plugin);
-        if (!is_a($plugin, 'PicoPluginInterface')) {
+        if (!($plugin instanceof PicoPluginInterface)) {
             throw new RuntimeException(
                 "Unable to load plugin '" . $className . "': "
                 . "Manually loaded plugins must implement 'PicoPluginInterface'"
@@ -1477,7 +1477,7 @@ class Pico
             foreach ($this->plugins as $plugin) {
                 // only trigger events for plugins that implement PicoPluginInterface
                 // deprecated events (plugins for Pico 0.9 and older) will be triggered by `PicoDeprecated`
-                if (is_a($plugin, 'PicoPluginInterface')) {
+                if ($plugin instanceof PicoPluginInterface) {
                     $plugin->handleEvent($eventName, $params);
                 }
             }
diff --git a/lib/PicoTwigExtension.php b/lib/PicoTwigExtension.php
index c249ff4..383330a 100644
--- a/lib/PicoTwigExtension.php
+++ b/lib/PicoTwigExtension.php
@@ -102,7 +102,7 @@ class PicoTwigExtension extends Twig_Extension
      */
     public function mapFilter($var, $mapKeyPath)
     {
-        if (!is_array($var) && (!is_object($var) || !is_a($var, 'Traversable'))) {
+        if (!is_array($var) && (!is_object($var) || !($var instanceof Traversable))) {
             throw new Twig_Error_Runtime(sprintf(
                 'The map filter only works with arrays or "Traversable", got "%s"',
                 is_object($var) ? get_class($var) : gettype($var)
@@ -141,7 +141,7 @@ class PicoTwigExtension extends Twig_Extension
      */
     public function sortByFilter($var, $sortKeyPath, $fallback = 'bottom')
     {
-        if (is_object($var) && is_a($var, 'Traversable')) {
+        if (is_object($var) && ($var instanceof Traversable)) {
             $var = iterator_to_array($var, true);
         } elseif (!is_array($var)) {
             throw new Twig_Error_Runtime(sprintf(
@@ -204,9 +204,9 @@ class PicoTwigExtension extends Twig_Extension
 
         foreach ($keyPath as $key) {
             if (is_object($var)) {
-                if (is_a($var, 'ArrayAccess')) {
+                if ($var instanceof ArrayAccess) {
                     // use ArrayAccess, see below
-                } elseif (is_a($var, 'Traversable')) {
+                } elseif ($var instanceof Traversable) {
                     $var = iterator_to_array($var);
                 } elseif (isset($var->{$key})) {
                     $var = $var->{$key};
diff --git a/plugins/00-PicoDeprecated.php b/plugins/00-PicoDeprecated.php
index 59600b4..e2db93a 100644
--- a/plugins/00-PicoDeprecated.php
+++ b/plugins/00-PicoDeprecated.php
@@ -68,7 +68,7 @@ class PicoDeprecated extends AbstractPicoPlugin
     {
         if (!empty($plugins)) {
             foreach ($plugins as $plugin) {
-                if (!is_a($plugin, 'PicoPluginInterface')) {
+                if (!($plugin instanceof PicoPluginInterface)) {
                     // the plugin doesn't implement PicoPluginInterface; it uses deprecated events
                     // enable PicoDeprecated if it hasn't be explicitly enabled/disabled yet
                     if (!$this->isStatusChanged()) {