diff --git a/visitor.php b/visitor.php
index 3050486..ba5d55e 100644
--- a/visitor.php
+++ b/visitor.php
@@ -383,7 +383,7 @@ private function postProcessNode(Node $node): void
 
         $newDocComment = $this->addTags($name, $docComment);
 
-        if ($newDocComment !== null) {
+        if ($newDocComment instanceof Doc) {
             $node->setDocComment($newDocComment);
         }
 
@@ -399,7 +399,7 @@ private function postProcessNode(Node $node): void
 
         $newDocComment = $this->addStringTags($name, $docComment);
 
-        if ($newDocComment !== null) {
+        if ($newDocComment instanceof Doc) {
             $node->setDocComment($newDocComment);
         }
     }
@@ -434,7 +434,7 @@ private function generateAdditionalTagsFromDoc(Doc $docComment): array
         foreach ($params as $param) {
             $addition = self::getAdditionFromParam($param);
 
-            if ($addition !== null) {
+            if ($addition instanceof WordPressTag) {
                 $additions[] = $addition;
             }
         }
@@ -442,7 +442,7 @@ private function generateAdditionalTagsFromDoc(Doc $docComment): array
         foreach ($returns as $return) {
             $addition = self::getAdditionFromReturn($return);
 
-            if ($addition !== null) {
+            if ($addition instanceof WordPressTag) {
                 $additions[] = $addition;
             }
         }
@@ -450,7 +450,7 @@ private function generateAdditionalTagsFromDoc(Doc $docComment): array
         foreach ($vars as $var) {
             $addition = self::getAdditionFromVar($var);
 
-            if ($addition !== null) {
+            if ($addition instanceof WordPressTag) {
                 $additions[] = $addition;
             }
         }
@@ -549,7 +549,7 @@ private function getInheritedTagsForParam(Param $param): array
     {
         $type = $param->getType();
 
-        if ($type === null) {
+        if (!$type instanceof Type) {
             return [];
         }
 
@@ -561,7 +561,7 @@ private function getInheritedTagsForParam(Param $param): array
 
         $paramDescription = $param->getDescription();
 
-        if ($paramDescription === null) {
+        if (!$paramDescription instanceof Description) {
             return [];
         }
 
@@ -587,7 +587,7 @@ private function getInheritedTagsForParam(Param $param): array
 
             $match = self::getMatchingInheritedTag($param, $tags, $symbolName);
 
-            if ($match !== null) {
+            if ($match instanceof WordPressTag) {
                 $additions[] = $match;
             }
         }
@@ -698,7 +698,7 @@ private function getAdditionFromParam(Param $tag): ?WordPressTag
         $tagVariableType = $tag->getType();
 
         // Skip if information we need is missing.
-        if (!$tagDescription || !$tagVariableName || !$tagVariableType) {
+        if (!$tagDescription instanceof Description || !$tagVariableName || !$tagVariableType instanceof Type) {
             return null;
         }
 
@@ -744,7 +744,7 @@ private function getAdditionFromReturn(Return_ $tag): ?WordPressTag
         $tagVariableType = $tag->getType();
 
         // Skip if information we need is missing.
-        if (!$tagDescription || !$tagVariableType) {
+        if (!$tagDescription instanceof Description || !$tagVariableType instanceof Type) {
             return null;
         }
 
@@ -784,7 +784,7 @@ private static function getAdditionFromVar(Var_ $tag): ?WordPressTag
         $tagVariableType = $tag->getType();
 
         // Skip if information we need is missing.
-        if (!$tagDescription || !$tagVariableType) {
+        if (!$tagDescription instanceof Description || !$tagVariableType instanceof Type) {
             return null;
         }
 
@@ -1008,7 +1008,7 @@ private function voidOrNever(Node $node): string
                     static function (Node $node): bool {
                         return isset($node->expr);
                     }
-                ) !== null
+                ) instanceof Node
             ) {
                 return '';
             }