diff --git a/detekt-api/src/test/kotlin/io/gitlab/arturbosch/detekt/api/internal/KotlinEnvironmentUtilsTest.kt b/detekt-api/src/test/kotlin/io/gitlab/arturbosch/detekt/api/internal/KotlinEnvironmentUtilsTest.kt
index 7ddb7c1e87b..2064e6aa4bc 100644
--- a/detekt-api/src/test/kotlin/io/gitlab/arturbosch/detekt/api/internal/KotlinEnvironmentUtilsTest.kt
+++ b/detekt-api/src/test/kotlin/io/gitlab/arturbosch/detekt/api/internal/KotlinEnvironmentUtilsTest.kt
@@ -21,7 +21,7 @@ class KotlinEnvironmentUtilsTest : Spek({
                 .toList()
 
             val languageVersion = classpathFiles.getKotlinLanguageVersion()
-            assertThat(languageVersion).isNotNull()
+            assertThat(languageVersion).isNotNull
             assertThat(languageVersion?.versionString).isEqualTo(expectedVersionString)
         }
     }
diff --git a/detekt-cli/src/main/kotlin/io/gitlab/arturbosch/detekt/cli/out/HtmlOutputReport.kt b/detekt-cli/src/main/kotlin/io/gitlab/arturbosch/detekt/cli/out/HtmlOutputReport.kt
index 5afd12fca28..533e831b640 100644
--- a/detekt-cli/src/main/kotlin/io/gitlab/arturbosch/detekt/cli/out/HtmlOutputReport.kt
+++ b/detekt-cli/src/main/kotlin/io/gitlab/arturbosch/detekt/cli/out/HtmlOutputReport.kt
@@ -31,11 +31,11 @@ class HtmlOutputReport : OutputReport() {
     }
 
     private fun renderFindings(findings: Map<String, List<Finding>>) = htmlSnippet {
-        for ((group, groupFindings) in findings.filter { !it.value.isEmpty() }) {
+        for ((group, groupFindings) in findings.filter { it.value.isNotEmpty() }) {
             h3 { group }
 
             groupFindings.groupBy { it.id }.forEach { rule, findings ->
-                if (!findings.isEmpty()) {
+                if (findings.isNotEmpty()) {
                     div("rule-container") {
                         span("rule") { rule }
                         span("description") { findings.first().issue.description }
@@ -45,7 +45,7 @@ class HtmlOutputReport : OutputReport() {
                 list(findings) {
                     span("location") { "${it.file}:${it.location.source.line}:${it.location.source.column}" }
 
-                    if (!it.message.isEmpty()) {
+                    if (it.message.isNotEmpty()) {
                         br()
                         span("message") { it.message }
                     }
diff --git a/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/SpacingBetweenPackageAndImports.kt b/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/SpacingBetweenPackageAndImports.kt
index 8db29440a4a..7666c593dd9 100644
--- a/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/SpacingBetweenPackageAndImports.kt
+++ b/detekt-rules/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/SpacingBetweenPackageAndImports.kt
@@ -67,7 +67,7 @@ class SpacingBetweenPackageAndImports(config: Config = Config.empty) : Rule(conf
             element is KtPackageDirective && element.text.isNotEmpty()
 
     private fun checkKtElementsDeclaration(importList: KtImportList) {
-        val ktElements = importList.siblings(withItself = false).toList().filter { it is KtElement }
+        val ktElements = importList.siblings(withItself = false).toList().filterIsInstance<KtElement>()
         val nextSibling = importList.nextSibling
         if (ktElements.isNotEmpty() &&
                 (nextSibling is PsiWhiteSpace || nextSibling is KtElement)) {