diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/GenerationState.java b/compiler/backend/src/org/jetbrains/jet/codegen/GenerationState.java
index a378304ac3d..db142585742 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/GenerationState.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/GenerationState.java
@@ -8,6 +8,7 @@ import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Pair;
 import com.intellij.psi.PsiElement;
 import com.intellij.util.containers.Stack;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.codegen.intrinsics.IntrinsicMethods;
 import org.jetbrains.jet.lang.cfg.pseudocode.JetControlFlowDataTraceFactory;
 import org.jetbrains.jet.lang.descriptors.ClassDescriptor;
@@ -23,6 +24,7 @@ import java.util.Collections;
 import java.util.List;
 
 public class GenerationState {
+    @NotNull
     private final ClassFileFactory factory;
     private final Project project;
 
@@ -38,6 +40,7 @@ public class GenerationState {
         this.intrinsics = new IntrinsicMethods(project, standardLibrary);
     }
 
+    @NotNull
     public ClassFileFactory getFactory() {
         return factory;
     }
diff --git a/compiler/backend/src/org/jetbrains/jet/compiler/CompileSession.java b/compiler/backend/src/org/jetbrains/jet/compiler/CompileSession.java
index 494291f1d52..282fe666fa7 100644
--- a/compiler/backend/src/org/jetbrains/jet/compiler/CompileSession.java
+++ b/compiler/backend/src/org/jetbrains/jet/compiler/CompileSession.java
@@ -4,6 +4,7 @@ import com.google.common.base.Predicates;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.PsiManager;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.JetCoreEnvironment;
 import org.jetbrains.jet.codegen.ClassBuilderFactory;
 import org.jetbrains.jet.codegen.ClassFileFactory;
@@ -107,6 +108,7 @@ public class CompileSession {
         return !errorCollector.hasErrors;
     }
 
+    @NotNull
     public ClassFileFactory generate() {
         GenerationState generationState = new GenerationState(myEnvironment.getProject(), ClassBuilderFactory.BINARIES);
         generationState.compileCorrectFiles(myBindingContext, mySourceFiles);
diff --git a/compiler/tests/org/jetbrains/jet/codegen/CodegenTestCase.java b/compiler/tests/org/jetbrains/jet/codegen/CodegenTestCase.java
index 28a91e2dafa..e29335cad53 100644
--- a/compiler/tests/org/jetbrains/jet/codegen/CodegenTestCase.java
+++ b/compiler/tests/org/jetbrains/jet/codegen/CodegenTestCase.java
@@ -1,6 +1,7 @@
 package org.jetbrains.jet.codegen;
 
 import com.intellij.openapi.util.text.StringUtil;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.JetLiteFixture;
 import org.jetbrains.jet.lang.psi.JetFile;
@@ -109,13 +110,13 @@ public abstract class CodegenTestCase extends JetLiteFixture {
         return loadRootNamespaceClass(state);
     }
 
-    protected Class loadRootNamespaceClass(ClassFileFactory state) {
+    protected Class loadRootNamespaceClass(@NotNull ClassFileFactory state) {
         String fqName = NamespaceCodegen.getJVMClassName(JetPsiUtil.getFQName(myFile)).replace("/", ".");
         Map<String, Class> classMap = loadAllClasses(state);
         return classMap.get(fqName);
     }
 
-    protected Class loadClass(String fqName, ClassFileFactory state) {
+    protected Class loadClass(String fqName, @NotNull ClassFileFactory state) {
         List<String> files = state.files();
         for (String file : files) {
             if (file.equals(fqName.replace('.', '/') + ".class")) {
@@ -128,7 +129,7 @@ public abstract class CodegenTestCase extends JetLiteFixture {
         return null;
     }
 
-    protected Map<String, Class> loadAllClasses(ClassFileFactory state) {
+    protected Map<String, Class> loadAllClasses(@NotNull ClassFileFactory state) {
         Map<String, Class> result = new HashMap<String, Class>();
         for (String fileName : state.files()) {
             String className = StringUtil.trimEnd(fileName, ".class").replace('/', '.');
@@ -139,6 +140,7 @@ public abstract class CodegenTestCase extends JetLiteFixture {
         return result;
     }
 
+    @NotNull
     protected ClassFileFactory generateClassesInFile() {
         try {
             GenerationState state = new GenerationState(getProject(), ClassBuilderFactory.BINARIES);
@@ -200,7 +202,7 @@ public abstract class CodegenTestCase extends JetLiteFixture {
         assertTrue(Math.abs(returnValue - currentTime) <= 1L);
     }
 
-    protected Class loadImplementationClass(ClassFileFactory codegens, final String name) {
+    protected Class loadImplementationClass(@NotNull ClassFileFactory codegens, final String name) {
         return loadClass(name, codegens);
     }
 
diff --git a/compiler/tests/org/jetbrains/jet/codegen/StdlibTest.java b/compiler/tests/org/jetbrains/jet/codegen/StdlibTest.java
index f16bdf4617b..434aa5106ca 100644
--- a/compiler/tests/org/jetbrains/jet/codegen/StdlibTest.java
+++ b/compiler/tests/org/jetbrains/jet/codegen/StdlibTest.java
@@ -1,5 +1,7 @@
 package org.jetbrains.jet.codegen;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.compiler.CompileEnvironment;
 import org.jetbrains.jet.compiler.CompileSession;
 
@@ -30,6 +32,7 @@ public class StdlibTest extends CodegenTestCase {
         return session.generateText();
     }
 
+    @NotNull
     protected ClassFileFactory generateClassesInFile() {
         try {
             CompileSession session = new CompileSession(myEnvironment);
@@ -38,7 +41,7 @@ public class StdlibTest extends CodegenTestCase {
             session.addStdLibSources(true);
 
             if (!session.analyze(System.out)) {
-                return null;
+                throw new RuntimeException();
             }
 
             return session.generate();