diff --git a/features/semantic-class-errors.feature b/features/semantic-class-errors.feature
new file mode 100644
index 0000000..a779f61
--- /dev/null
+++ b/features/semantic-class-errors.feature
@@ -0,0 +1,32 @@
+Feature: Semantic errors in classes
+    As a user
+    I want all semantic invalid classes to be excluded from index
+    So that I can have project with broken classes or deps
+
+    Scenario: Class extending itself
+        Given there is a file with:
+        """
+        <?php
+
+        class C extends C {}
+        """
+
+    Scenario: Parent extends Child
+        Given there is a file with:
+        """
+        <?php
+
+        class E extends F {}
+        class F extends E {}
+        """
+
+    Scenario: Parent extends Sub Child
+        Given there is a file with:
+        """
+        <?php
+
+        class G extends H {}
+        class H extends I {}
+        class I extends G {}
+        """
+
diff --git a/src/Padawan/Domain/Project/Node/ClassData.php b/src/Padawan/Domain/Project/Node/ClassData.php
index ce9a8e9..74ae67b 100644
--- a/src/Padawan/Domain/Project/Node/ClassData.php
+++ b/src/Padawan/Domain/Project/Node/ClassData.php
@@ -2,11 +2,12 @@
 
 namespace Padawan\Domain\Project\Node;
 
-use Padawan\Domain\Project\FQCN;
 use Padawan\Domain\Project\FQN;
+use Padawan\Domain\Project\FQCN;
+use Padawan\Parser\Exception\SemanticError;
+use Padawan\Domain\Project\Collection\ConstCollection;
 use Padawan\Domain\Project\Collection\MethodsCollection;
 use Padawan\Domain\Project\Collection\PropertiesCollection;
-use Padawan\Domain\Project\Collection\ConstCollection;
 
 /**
  * @property $properties
@@ -64,7 +65,7 @@ public function getName()
     public function setParent($parent)
     {
         if ($this === $parent) {
-            throw new \Exception("Parent class and child class could not be same");
+            throw new SemanticError("Parent class and child class could not be same");
         }
         $this->parent = null;
         if ($parent instanceof ClassData) {
diff --git a/src/Padawan/Framework/Domain/Project/InMemoryIndex.php b/src/Padawan/Framework/Domain/Project/InMemoryIndex.php
index 2e1dd2c..8b1e019 100644
--- a/src/Padawan/Framework/Domain/Project/InMemoryIndex.php
+++ b/src/Padawan/Framework/Domain/Project/InMemoryIndex.php
@@ -181,6 +181,9 @@ public function getFunctions()
     }
 
     public function addClass(ClassData $class) {
+        if (!$this->isSemanticsCorrect($class)) {
+            return;
+        }
         $this->classes[$class->fqcn->toString()] = $class;
         if ($class->getParent() instanceof FQCN) {
             $this->addExtend($class, $class->getParent());
@@ -238,4 +241,15 @@ private function hasCoreIndex()
     {
         return $this !== self::$coreIndex && !empty(self::$coreIndex);
     }
+
+    private function isSemanticsCorrect(ClassData $class)
+    {
+        if ($class->getParent() === $class) {
+            return false;
+        }
+        if ($class->getParent() instanceof FQCN
+            && $class->getParent()->toString() === $class->fqcn->toString()) {
+            return false;
+        }
+    }
 }
diff --git a/src/Padawan/Parser/Exception/SemanticError.php b/src/Padawan/Parser/Exception/SemanticError.php
new file mode 100644
index 0000000..8bcce95
--- /dev/null
+++ b/src/Padawan/Parser/Exception/SemanticError.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Padawan\Parser\Exception;
+
+use Exception;
+
+/**
+ * Class SemanticError
+ * @author mkusher
+ */
+class SemanticError extends Exception
+{
+}