diff --git a/plugin/src/main/kotlin/org/kotlin/formatter/plugin/KotlinFormatterPlugin.kt b/plugin/src/main/kotlin/org/kotlin/formatter/plugin/KotlinFormatterPlugin.kt
index da31bcd..f8698cd 100644
--- a/plugin/src/main/kotlin/org/kotlin/formatter/plugin/KotlinFormatterPlugin.kt
+++ b/plugin/src/main/kotlin/org/kotlin/formatter/plugin/KotlinFormatterPlugin.kt
@@ -1,5 +1,6 @@
 package org.kotlin.formatter.plugin
 
+import java.io.File
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.jetbrains.kotlin.gradle.dsl.KotlinProjectExtension
@@ -15,9 +16,9 @@ class KotlinFormatterPlugin : Plugin<Project> {
             .register("formatKotlin", FormatKotlinTask::class.java) {
                 it.source(
                     target.extensions
-                        .getByType(KotlinProjectExtension::class.java)
-                        .sourceSets
-                        .flatMap { set -> set.kotlin.sourceDirectories.files }
+                        .findByType(KotlinProjectExtension::class.java)
+                        ?.sourceSets
+                        ?.flatMap { set -> set.kotlin.sourceDirectories.files } ?: setOf<File>()
                 )
             }
     }
diff --git a/plugin/src/test/kotlin/org/kotlin/formatter/plugin/FormatKotlinTaskTest.kt b/plugin/src/test/kotlin/org/kotlin/formatter/plugin/FormatKotlinTaskTest.kt
index 7e1353a..738711c 100644
--- a/plugin/src/test/kotlin/org/kotlin/formatter/plugin/FormatKotlinTaskTest.kt
+++ b/plugin/src/test/kotlin/org/kotlin/formatter/plugin/FormatKotlinTaskTest.kt
@@ -9,6 +9,7 @@ import org.gradle.testkit.runner.TaskOutcome
 import org.gradle.util.GFileUtils.parentMkdirs
 import org.gradle.util.GFileUtils.writeFile
 import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.io.TempDir
 
@@ -17,99 +18,118 @@ class FormatKotlinTaskTest {
     lateinit var testFolder: Path
 
     @BeforeEach
-    fun setup() {
-        writeBuildScript()
-        writeSettingsFile()
-    }
-
-    private fun writeBuildScript() {
-        writeFile(
-            """
-                plugins {
-                    kotlin("jvm") version "1.3.72"
-                    id("tech.formatter-kt.formatter")
-                }
-            """.trimIndent(),
-            testFolder.resolve("build.gradle.kts").toFile()
-        )
-    }
-
-    private fun writeSettingsFile() {
+    fun writeSettingsFile() {
         writeFile(
             """rootProject.name = "test"""".trimIndent(),
             testFolder.resolve("settings.gradle.kts").toFile()
         )
     }
 
-    @Test
-    fun `should format Kotlin source files`() {
-        val sourceDirectory = testFolder.resolve("src/main/kotlin/somepackage")
-        val sourceFile = sourceDirectory.resolve("AClass.kt")
-        parentMkdirs(sourceDirectory.toFile())
-        writeFile(
-            """
-                package somepackage
-                
-                class  AClass {
-                val aProperty:
-                String = "Hello"
-                }
-            """.trimIndent(),
-            sourceFile.toFile()
-        )
-
-        runFormatter()
+    @Nested
+    inner class WithKotlinPlugin {
+        @BeforeEach
+        fun writeBuildScript() {
+            writeFile(
+                """
+                    plugins {
+                        kotlin("jvm") version "1.3.72"
+                        id("tech.formatter-kt.formatter")
+                    }
+                """.trimIndent(),
+                testFolder.resolve("build.gradle.kts").toFile()
+            )
+        }
 
-        assertThat(Files.readString(sourceFile))
-            .isEqualTo(
+        @Test
+        fun `should format Kotlin source files`() {
+            val sourceDirectory = testFolder.resolve("src/main/kotlin/somepackage")
+            val sourceFile = sourceDirectory.resolve("AClass.kt")
+            parentMkdirs(sourceDirectory.toFile())
+            writeFile(
                 """
                     package somepackage
                     
-                    class AClass {
-                        val aProperty: String = "Hello"
+                    class  AClass {
+                    val aProperty:
+                    String = "Hello"
                     }
-                """.trimIndent()
+                """.trimIndent(),
+                sourceFile.toFile()
             )
-    }
 
-    @Test
-    fun `should not format Java source files`() {
-        val sourceDirectory = testFolder.resolve("src/main/kotlin/somepackage")
-        writeKotlinSourceFile("AnotherClass", sourceDirectory)
-        val sourceFile = sourceDirectory.resolve("AClass.java")
-        parentMkdirs(sourceDirectory.toFile())
-        writeFile(
-            """
-                package somepackage;
-                public class  AClass { String aProperty =
-                "Hello"; }
-            """.trimIndent(),
-            sourceFile.toFile()
-        )
+            runFormatter()
 
-        val result = runFormatter()
+            assertThat(Files.readString(sourceFile))
+                .isEqualTo(
+                    """
+                        package somepackage
+                        
+                        class AClass {
+                            val aProperty: String = "Hello"
+                        }
+                    """.trimIndent()
+                )
+        }
 
-        assertThat(result.task(":formatKotlin")?.outcome).isEqualTo(TaskOutcome.SUCCESS)
-        assertThat(Files.readString(sourceFile))
-            .isEqualTo(
+        @Test
+        fun `should not format Java source files`() {
+            val sourceDirectory = testFolder.resolve("src/main/kotlin/somepackage")
+            writeKotlinSourceFile("AnotherClass", sourceDirectory)
+            val sourceFile = sourceDirectory.resolve("AClass.java")
+            parentMkdirs(sourceDirectory.toFile())
+            writeFile(
                 """
                     package somepackage;
                     public class  AClass { String aProperty =
                     "Hello"; }
-                """.trimIndent()
+                """.trimIndent(),
+                sourceFile.toFile()
             )
+
+            val result = runFormatter()
+
+            assertThat(result.task(":formatKotlin")?.outcome).isEqualTo(TaskOutcome.SUCCESS)
+            assertThat(Files.readString(sourceFile))
+                .isEqualTo(
+                    """
+                        package somepackage;
+                        public class  AClass { String aProperty =
+                        "Hello"; }
+                    """.trimIndent()
+                )
+        }
+
+        private fun writeKotlinSourceFile(className: String, sourceDirectory: Path) {
+            val sourceFile = sourceDirectory.resolve("$className.kt")
+            writeFile(
+                """
+                    package somepackage
+                    
+                    class $className
+                """.trimIndent(),
+                sourceFile.toFile()
+            )
+        }
     }
 
-    private fun writeKotlinSourceFile(className: String, sourceDirectory: Path) {
-        val sourceFile = sourceDirectory.resolve("$className.kt")
-        writeFile(
-            """
-                package somepackage
-                
-                class $className
-            """.trimIndent(),
-            sourceFile.toFile()
-        )
+    @Nested
+    inner class WithoutKotlinPlugin {
+        @Test
+        fun `should skip task if Kotlin plugin was not applied`() {
+            writeFile(
+                """
+                    plugins {
+                        java
+                        id("tech.formatter-kt.formatter")
+                    }
+                """.trimIndent(),
+                testFolder.resolve("build.gradle.kts").toFile()
+            )
+
+            val result = runFormatter()
+
+            assertThat(result.task(":formatKotlin")?.outcome).isEqualTo(TaskOutcome.NO_SOURCE)
+        }
     }
 
     private fun runFormatter(): BuildResult {