diff --git a/module/VuFind/src/VuFind/Search/BackendManager.php b/module/VuFind/src/VuFind/Search/BackendManager.php
index 16364ff107136c5f257e1aadab45eb5a7064d751..5da1cc3e4908620f8d38f077ef83fc8ef1ee5a93 100644
--- a/module/VuFind/src/VuFind/Search/BackendManager.php
+++ b/module/VuFind/src/VuFind/Search/BackendManager.php
@@ -110,7 +110,7 @@ class BackendManager implements SharedListenerAggregateInterface
                 )
             );
         }
-        if (!$backend instanceOf BackendInterface) {
+        if (!$backend instanceof BackendInterface) {
             throw new UnexpectedValueException(
                 sprintf(
                     'Object of class %s does not implement the expected interface',
diff --git a/module/VuFind/src/VuFind/Search/Solr/V3/ErrorListener.php b/module/VuFind/src/VuFind/Search/Solr/V3/ErrorListener.php
index 5133f75b27ee3b276e0f37d03fa9d99929b5eff5..43b38859b74cc474f4c8756f0bbb6b2ea08d21e3 100644
--- a/module/VuFind/src/VuFind/Search/Solr/V3/ErrorListener.php
+++ b/module/VuFind/src/VuFind/Search/Solr/V3/ErrorListener.php
@@ -58,7 +58,7 @@ class ErrorListener extends AbstractErrorListener
         $backend = $event->getParam('backend_instance');
         if ($this->listenForBackend($backend)) {
             $error  = $event->getTarget();
-            if ($error instanceOf HttpErrorException) {
+            if ($error instanceof HttpErrorException) {
                 $reason = $error->getResponse()->getReasonPhrase();
                 if (stristr($reason, 'org.apache.lucene.queryParser.ParseException')
                     || stristr($reason, 'undefined field')
diff --git a/module/VuFind/src/VuFind/Search/Solr/V4/ErrorListener.php b/module/VuFind/src/VuFind/Search/Solr/V4/ErrorListener.php
index af6fa05ce86d30b9fa4041bf006845a198c9ffb7..759322efd4b6e04df1f5347bdffc9dda81cf8ef9 100644
--- a/module/VuFind/src/VuFind/Search/Solr/V4/ErrorListener.php
+++ b/module/VuFind/src/VuFind/Search/Solr/V4/ErrorListener.php
@@ -68,7 +68,7 @@ class ErrorListener extends AbstractErrorListener
         $backend = $event->getParam('backend_instance');
         if ($this->listenForBackend($backend)) {
             $error = $event->getTarget();
-            if ($error instanceOf HttpErrorException) {
+            if ($error instanceof HttpErrorException) {
                 $response = $error->getResponse();
 
                 $body = $response->getBody();
diff --git a/module/VuFindSearch/src/VuFindSearch/Backend/Solr/Connector.php b/module/VuFindSearch/src/VuFindSearch/Backend/Solr/Connector.php
index c3eb4fd8c37ef73dfb1f9fdf63eb97e962c80e6f..eac4a1b3e04ee4c0530f94e31773e438c70f79d7 100644
--- a/module/VuFindSearch/src/VuFindSearch/Backend/Solr/Connector.php
+++ b/module/VuFindSearch/src/VuFindSearch/Backend/Solr/Connector.php
@@ -322,7 +322,7 @@ class Connector implements \Zend\Log\LoggerAwareInterface
      */
     public function setAdapter($adapter)
     {
-        if (is_object($adapter) && (!$adapter instanceOf AdapterInterface)) {
+        if (is_object($adapter) && (!$adapter instanceof AdapterInterface)) {
             throw new InvalidArgumentException(
                 sprintf(
                     'HTTP client adapter must implement AdapterInterface: %s',
diff --git a/module/VuFindSearch/src/VuFindSearch/Backend/Solr/QueryBuilder.php b/module/VuFindSearch/src/VuFindSearch/Backend/Solr/QueryBuilder.php
index 381b9bb804def44ad7eeb48d78c1f2324face000..a66804066ccd843399e41845a271d6f08ecb9c1a 100644
--- a/module/VuFindSearch/src/VuFindSearch/Backend/Solr/QueryBuilder.php
+++ b/module/VuFindSearch/src/VuFindSearch/Backend/Solr/QueryBuilder.php
@@ -126,7 +126,7 @@ class QueryBuilder implements QueryBuilderInterface
             $params->set('spellcheck.q', $query->getAllTerms());
         }
 
-        if ($query instanceOf QueryGroup) {
+        if ($query instanceof QueryGroup) {
             $query = $this->reduceQueryGroup($query);
         } else {
             $query->setString(
@@ -305,7 +305,7 @@ class QueryBuilder implements QueryBuilderInterface
      */
     protected function reduceQueryGroupComponents(AbstractQuery $component)
     {
-        if ($component instanceOf QueryGroup) {
+        if ($component instanceof QueryGroup) {
             $reduced = array_map(
                 array($this, 'reduceQueryGroupComponents'), $component->getQueries()
             );
diff --git a/module/VuFindSearch/src/VuFindSearch/Service.php b/module/VuFindSearch/src/VuFindSearch/Service.php
index 848684a705e294e8def71dd42dcfab33bfe41e7c..8885e90c01e5f6f89b2b231d225ca828fa99df3c 100644
--- a/module/VuFindSearch/src/VuFindSearch/Service.php
+++ b/module/VuFindSearch/src/VuFindSearch/Service.php
@@ -355,7 +355,7 @@ class Service
                 $this,
                 $args,
                 function ($o) {
-                    return ($o instanceOf BackendInterface);
+                    return ($o instanceof BackendInterface);
                 }
             );
             if (!$response->stopped()) {