diff --git a/compiler/cli/src/org/jetbrains/kotlin/cli/common/CLICompiler.java b/compiler/cli/src/org/jetbrains/kotlin/cli/common/CLICompiler.java
index 53ca95177fa..aef1f8195dc 100644
--- a/compiler/cli/src/org/jetbrains/kotlin/cli/common/CLICompiler.java
+++ b/compiler/cli/src/org/jetbrains/kotlin/cli/common/CLICompiler.java
@@ -39,6 +39,7 @@ import org.jetbrains.kotlin.config.Services;
 import org.jetbrains.kotlin.progress.CompilationCanceledException;
 import org.jetbrains.kotlin.progress.CompilationCanceledStatus;
 import org.jetbrains.kotlin.progress.ProgressIndicatorAndCompilationCanceledStatus;
+import org.jetbrains.kotlin.utils.StringsKt;
 
 import java.io.PrintStream;
 import java.util.List;
@@ -245,10 +246,18 @@ public abstract class CLICompiler<A extends CommonCompilerArguments> {
         }
 
         if (arguments.languageVersion != null) {
-            configuration.put(
-                    CommonConfigurationKeys.LANGUAGE_FEATURE_SETTINGS,
-                    LanguageFeatureSettings.fromLanguageVersion(arguments.languageVersion)
-            );
+            LanguageFeatureSettings languageFeatureSettings = LanguageFeatureSettings.fromLanguageVersion(arguments.languageVersion);
+            if (languageFeatureSettings != null) {
+                configuration.put(CommonConfigurationKeys.LANGUAGE_FEATURE_SETTINGS, languageFeatureSettings);
+            }
+            else {
+                String message =
+                        "Unknown language version: " + arguments.languageVersion + "\n" +
+                        "Supported language versions: " + StringsKt.join(LanguageFeatureSettings.getAllLanguageVersions(), ", ");
+                configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY).report(
+                        CompilerMessageSeverity.ERROR, message, CompilerMessageLocation.NO_LOCATION
+                );
+            }
         }
     }
 
diff --git a/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/K2JVMCompiler.kt b/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/K2JVMCompiler.kt
index 39ef8df5e40..0f83affcac4 100644
--- a/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/K2JVMCompiler.kt
+++ b/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/K2JVMCompiler.kt
@@ -221,10 +221,11 @@ class K2JVMCompiler : CLICompiler<K2JVMCompilerArguments>() {
             configuration: CompilerConfiguration, arguments: K2JVMCompilerArguments, services: Services
     ) {
         if (IncrementalCompilation.isEnabled()) {
-            configuration.put(
-                    JVMConfigurationKeys.INCREMENTAL_COMPILATION_COMPONENTS,
-                    services.get(IncrementalCompilationComponents::class.java)
-            )
+            val components = services.get(IncrementalCompilationComponents::class.java)
+            @Suppress("SENSELESS_COMPARISON")
+            if (components != null) {
+                configuration.put(JVMConfigurationKeys.INCREMENTAL_COMPILATION_COMPONENTS, components)
+            }
         }
     }
 
@@ -283,10 +284,11 @@ class K2JVMCompiler : CLICompiler<K2JVMCompilerArguments>() {
             configuration.put(JVMConfigurationKeys.DISABLE_CALL_ASSERTIONS, arguments.noCallAssertions)
             configuration.put(JVMConfigurationKeys.DISABLE_PARAM_ASSERTIONS, arguments.noParamAssertions)
             configuration.put(JVMConfigurationKeys.DISABLE_OPTIMIZATION, arguments.noOptimize)
-            configuration.put(JVMConfigurationKeys.DECLARATIONS_JSON_PATH, arguments.declarationsOutputPath)
             configuration.put(JVMConfigurationKeys.INHERIT_MULTIFILE_PARTS, arguments.inheritMultifileParts)
             configuration.put(CLIConfigurationKeys.ALLOW_KOTLIN_PACKAGE, arguments.allowKotlinPackage)
             configuration.put(CLIConfigurationKeys.REPORT_PERF, arguments.reportPerf)
+
+            arguments.declarationsOutputPath?.let { configuration.put(JVMConfigurationKeys.DECLARATIONS_JSON_PATH, it) }
         }
 
         private fun getClasspath(paths: KotlinPaths, arguments: K2JVMCompilerArguments): List<File> {
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/config/CompilerConfiguration.java b/compiler/frontend/src/org/jetbrains/kotlin/config/CompilerConfiguration.java
index 634f1926db8..f841f093e3b 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/config/CompilerConfiguration.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/config/CompilerConfiguration.java
@@ -62,7 +62,7 @@ public class CompilerConfiguration {
         return data == null ? Collections.<T>emptyList() : data;
     }
 
-    public <T> void put(@NotNull CompilerConfigurationKey<T> key, @Nullable T value) {
+    public <T> void put(@NotNull CompilerConfigurationKey<T> key, @NotNull T value) {
         checkReadOnly();
         map.put(key.ideaKey, value);
     }
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/config/LanguageFeatureSettings.kt b/compiler/frontend/src/org/jetbrains/kotlin/config/LanguageFeatureSettings.kt
index 67ade88b0ca..b12f937fe04 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/config/LanguageFeatureSettings.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/config/LanguageFeatureSettings.kt
@@ -39,5 +39,8 @@ class LanguageFeatureSettings(
 
         @JvmStatic
         fun fromLanguageVersion(source: String): LanguageFeatureSettings? = SETTINGS[source]
+
+        @JvmStatic
+        fun getAllLanguageVersions(): List<String> = SETTINGS.keys.toList()
     }
 }
diff --git a/compiler/testData/cli/js/languageVersion.args b/compiler/testData/cli/js/languageVersion.args
new file mode 100644
index 00000000000..377825bbeeb
--- /dev/null
+++ b/compiler/testData/cli/js/languageVersion.args
@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/languageVersion.kt
+-output
+$TEMP_DIR$/out.js
+-language-version
+1.0
diff --git a/compiler/testData/cli/js/languageVersion.kt b/compiler/testData/cli/js/languageVersion.kt
new file mode 100644
index 00000000000..73d94ad88be
--- /dev/null
+++ b/compiler/testData/cli/js/languageVersion.kt
@@ -0,0 +1,5 @@
+package test
+
+sealed class Base
+
+class Derived : Base()
diff --git a/compiler/testData/cli/js/languageVersion.out b/compiler/testData/cli/js/languageVersion.out
new file mode 100644
index 00000000000..d0066724501
--- /dev/null
+++ b/compiler/testData/cli/js/languageVersion.out
@@ -0,0 +1,4 @@
+compiler/testData/cli/js/languageVersion.kt:5:17: error: this type is sealed, so it can be inherited by only its own nested classes or objects
+class Derived : Base()
+                ^
+COMPILATION_ERROR
diff --git a/compiler/testData/cli/jvm/languageVersion.args b/compiler/testData/cli/jvm/languageVersion.args
new file mode 100644
index 00000000000..2b0e3d5e862
--- /dev/null
+++ b/compiler/testData/cli/jvm/languageVersion.args
@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/languageVersion.kt
+-d
+$TEMP_DIR$
+-language-version
+1.0
diff --git a/compiler/testData/cli/jvm/languageVersion.kt b/compiler/testData/cli/jvm/languageVersion.kt
new file mode 100644
index 00000000000..73d94ad88be
--- /dev/null
+++ b/compiler/testData/cli/jvm/languageVersion.kt
@@ -0,0 +1,5 @@
+package test
+
+sealed class Base
+
+class Derived : Base()
diff --git a/compiler/testData/cli/jvm/languageVersion.out b/compiler/testData/cli/jvm/languageVersion.out
new file mode 100644
index 00000000000..cdd464da409
--- /dev/null
+++ b/compiler/testData/cli/jvm/languageVersion.out
@@ -0,0 +1,4 @@
+compiler/testData/cli/jvm/languageVersion.kt:5:17: error: this type is sealed, so it can be inherited by only its own nested classes or objects
+class Derived : Base()
+                ^
+COMPILATION_ERROR
diff --git a/compiler/testData/cli/jvm/languageVersionInvalid.args b/compiler/testData/cli/jvm/languageVersionInvalid.args
new file mode 100644
index 00000000000..26050e77cc3
--- /dev/null
+++ b/compiler/testData/cli/jvm/languageVersionInvalid.args
@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/simple.kt
+-d
+$TEMP_DIR$
+-language-version
+239.42
diff --git a/compiler/testData/cli/jvm/languageVersionInvalid.out b/compiler/testData/cli/jvm/languageVersionInvalid.out
new file mode 100644
index 00000000000..309af4defbb
--- /dev/null
+++ b/compiler/testData/cli/jvm/languageVersionInvalid.out
@@ -0,0 +1,3 @@
+error: unknown language version: 239.42
+Supported language versions: 1.0, 1.1
+COMPILATION_ERROR
\ No newline at end of file
diff --git a/compiler/tests/org/jetbrains/kotlin/cli/CliTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/cli/CliTestGenerated.java
index cc45a2d6963..3a5cfb04657 100644
--- a/compiler/tests/org/jetbrains/kotlin/cli/CliTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/cli/CliTestGenerated.java
@@ -151,6 +151,18 @@ public class CliTestGenerated extends AbstractCliTest {
             doJvmTest(fileName);
         }
 
+        @TestMetadata("languageVersion.args")
+        public void testLanguageVersion() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/cli/jvm/languageVersion.args");
+            doJvmTest(fileName);
+        }
+
+        @TestMetadata("languageVersionInvalid.args")
+        public void testLanguageVersionInvalid() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/cli/jvm/languageVersionInvalid.args");
+            doJvmTest(fileName);
+        }
+
         @TestMetadata("multipleTextRangesInDiagnosticsOrder.args")
         public void testMultipleTextRangesInDiagnosticsOrder() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/cli/jvm/multipleTextRangesInDiagnosticsOrder.args");
@@ -340,6 +352,12 @@ public class CliTestGenerated extends AbstractCliTest {
             doJsTest(fileName);
         }
 
+        @TestMetadata("languageVersion.args")
+        public void testLanguageVersion() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/cli/js/languageVersion.args");
+            doJsTest(fileName);
+        }
+
         @TestMetadata("libraryDirNotFound.args")
         public void testLibraryDirNotFound() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/cli/js/libraryDirNotFound.args");