diff --git a/detekt-rules-naming/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNaming.kt b/detekt-rules-naming/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNaming.kt
index 63f1bfabca0..fe2322353e6 100644
--- a/detekt-rules-naming/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNaming.kt
+++ b/detekt-rules-naming/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNaming.kt
@@ -10,6 +10,7 @@ import io.gitlab.arturbosch.detekt.api.config
 import io.gitlab.arturbosch.detekt.rules.identifierName
 import io.gitlab.arturbosch.detekt.rules.isConstant
 import org.jetbrains.kotlin.psi.KtProperty
+import org.jetbrains.kotlin.psi.psiUtil.isExtensionDeclaration
 import org.jetbrains.kotlin.psi.psiUtil.isPrivate
 
 /**
@@ -32,7 +33,8 @@ class TopLevelPropertyNaming(config: Config) : Rule(
 
     override fun visitProperty(property: KtProperty) {
         super.visitProperty(property)
-        if (!property.isTopLevel) return
+        if (!property.isTopLevel || property.psiOrParent.isExtensionDeclaration()) return
+
         if (property.isConstant()) {
             handleConstant(property)
         } else {
diff --git a/detekt-rules-naming/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNamingSpec.kt b/detekt-rules-naming/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNamingSpec.kt
index 79933b043ba..9cc14158920 100644
--- a/detekt-rules-naming/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNamingSpec.kt
+++ b/detekt-rules-naming/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/naming/TopLevelPropertyNamingSpec.kt
@@ -46,6 +46,15 @@ class TopLevelPropertyNamingSpec {
         }
     }
 
+    @Test
+    fun `should not report on top level extension properties`() {
+        val code = """
+            val String._foo = "foo"
+        """.trimIndent()
+
+        assertThat(subject.lint(code)).isEmpty()
+    }
+
     @Nested
     inner class `variables on top level` {