diff --git a/compiler/util/src/org/jetbrains/jet/utils/PathUtil.java b/compiler/util/src/org/jetbrains/jet/utils/PathUtil.java
index 4df763b3c6e..0109a244e5d 100644
--- a/compiler/util/src/org/jetbrains/jet/utils/PathUtil.java
+++ b/compiler/util/src/org/jetbrains/jet/utils/PathUtil.java
@@ -139,6 +139,7 @@ public class PathUtil {
         }
     }
 
+    @NotNull
     public static File findRtJar() {
         String javaHome = System.getProperty("java.home");
         if ("jre".equals(new File(javaHome).getName())) {
diff --git a/libraries/tools/kdoc/src/main/kotlin/org/jetbrains/kotlin/doc/KDocCompiler.kt b/libraries/tools/kdoc/src/main/kotlin/org/jetbrains/kotlin/doc/KDocCompiler.kt
index f5aa0c1ae4a..25101a30ad4 100644
--- a/libraries/tools/kdoc/src/main/kotlin/org/jetbrains/kotlin/doc/KDocCompiler.kt
+++ b/libraries/tools/kdoc/src/main/kotlin/org/jetbrains/kotlin/doc/KDocCompiler.kt
@@ -10,7 +10,7 @@ import org.jetbrains.jet.config.CompilerConfiguration
 /**
 * Main for running the KDocCompiler
 */
-fun main(args: Array<String?>): Unit {
+fun main(args: Array<String>): Unit {
     CLICompiler.doMain(KDocCompiler(), args);
 }
 
diff --git a/libraries/tools/kdoc/src/test/kotlin/test/kotlin/kdoc/KDocTest.kt b/libraries/tools/kdoc/src/test/kotlin/test/kotlin/kdoc/KDocTest.kt
index eada2ec9fbf..a7f7c17036b 100644
--- a/libraries/tools/kdoc/src/test/kotlin/test/kotlin/kdoc/KDocTest.kt
+++ b/libraries/tools/kdoc/src/test/kotlin/test/kotlin/kdoc/KDocTest.kt
@@ -25,7 +25,7 @@ class KDocTest {
 
         val args = KDocArguments()
         //args.setModule(moduleName)
-        val sourceDirs = ArrayList<String?>()
+        val sourceDirs = ArrayList<String>()
         sourceDirs.add("../../stdlib/src")
         sourceDirs.add("../../kunit/src/main/kotlin")
         sourceDirs.add("../../kotlin-jdbc/src/main/kotlin")
@@ -35,7 +35,7 @@ class KDocTest {
         args.setClasspath("../runtime/target/kotlin-runtime-0.1-SNAPSHOT.jar${File.pathSeparator}../../lib/junit-4.9.jar")
 
         val config = args.docConfig
-        config.docOutputDir = outDir.toString()!!
+        config.docOutputDir = outDir.toString()
         config.title = "Kotlin API"
 
         val ignorePackages = config.ignorePackages