diff --git a/grammar/php7.y b/grammar/php7.y
index d20e069af5..17db19f226 100644
--- a/grammar/php7.y
+++ b/grammar/php7.y
@@ -387,7 +387,7 @@ class_entry_type:
 
 class_modifiers:
       class_modifier                                        { $$ = $1; }
-    | class_modifiers class_modifier                        { $this->checkModifier($1, $2, #2); $$ = $1 | $2; }
+    | class_modifiers class_modifier                        { $this->checkClassModifier($1, $2, #2); $$ = $1 | $2; }
 ;
 
 class_modifier:
diff --git a/lib/PhpParser/Node/Stmt/Class_.php b/lib/PhpParser/Node/Stmt/Class_.php
index d5b39b5489..52ed6c6cd6 100644
--- a/lib/PhpParser/Node/Stmt/Class_.php
+++ b/lib/PhpParser/Node/Stmt/Class_.php
@@ -81,6 +81,27 @@ public function isAnonymous() : bool {
         return null === $this->name;
     }
 
+    /**
+     * @internal
+     */
+    public static function verifyClassModifier($a, $b) {
+        if ($a & self::MODIFIER_ABSTRACT && $b & self::MODIFIER_ABSTRACT) {
+            throw new Error('Multiple abstract modifiers are not allowed');
+        }
+
+        if ($a & self::MODIFIER_FINAL && $b & self::MODIFIER_FINAL) {
+            throw new Error('Multiple final modifiers are not allowed');
+        }
+
+        if ($a & self::MODIFIER_READONLY && $b & self::MODIFIER_READONLY) {
+            throw new Error('Multiple readonly modifiers are not allowed');
+        }
+
+        if ($a & 48 && $b & 48) {
+            throw new Error('Cannot use the final modifier on an abstract class');
+        }
+    }
+
     /**
      * @internal
      */
diff --git a/lib/PhpParser/ParserAbstract.php b/lib/PhpParser/ParserAbstract.php
index 5ee5a64bbd..29fa8de424 100644
--- a/lib/PhpParser/ParserAbstract.php
+++ b/lib/PhpParser/ParserAbstract.php
@@ -875,6 +875,10 @@ protected function createCommentNopAttributes(array $comments) {
         return $attributes;
     }
 
+    protected function checkClassModifier($a, $b, $modifierPos) {
+        Class_::verifyClassModifier($a, $b);
+    }
+
     protected function checkModifier($a, $b, $modifierPos) {
         // Jumping through some hoops here because verifyModifier() is also used elsewhere
         try {