diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderer.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderer.kt
index a440598e486..0a1869d27d6 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderer.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderer.kt
@@ -7,13 +7,12 @@ package org.jetbrains.kotlin.fir.analysis.diagnostics
 
 import org.jetbrains.kotlin.diagnostics.rendering.*
 import org.jetbrains.kotlin.fir.FirSourceElement
-import java.text.MessageFormat
 
-sealed class FirDiagnosticRenderer<D : FirDiagnostic<*>> : DiagnosticRenderer<D> {
-    abstract override fun render(diagnostic: D): String
+interface FirDiagnosticRenderer<D : FirDiagnostic<*>> : DiagnosticRenderer<D> {
+    override fun render(diagnostic: D): String
 }
 
-class SimpleFirDiagnosticRenderer<E : FirSourceElement>(private val message: String) : FirDiagnosticRenderer<FirSimpleDiagnostic<E>>() {
+class SimpleFirDiagnosticRenderer<E : FirSourceElement>(private val message: String) : FirDiagnosticRenderer<FirSimpleDiagnostic<E>> {
     override fun render(diagnostic: FirSimpleDiagnostic<E>): String {
         return message
     }
@@ -21,15 +20,7 @@ class SimpleFirDiagnosticRenderer<E : FirSourceElement>(private val message: Str
 
 sealed class AbstractFirDiagnosticWithParametersRenderer<D : FirDiagnostic<*>>(
     protected val message: String
-) : FirDiagnosticRenderer<D>() {
-    private val messageFormat = MessageFormat(message)
-
-    override fun render(diagnostic: D): String {
-        return messageFormat.format(renderParameters(diagnostic))
-    }
-
-    abstract fun renderParameters(diagnostic: D): Array<out Any>
-}
+) : FirDiagnosticRenderer<D>, AbstractDiagnosticWithParametersRenderer<D>(message)
 
 class FirDiagnosticWithParameters1Renderer<E : FirSourceElement, A : Any>(
     message: String,
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt
index 3dcac178b75..163207c7b84 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/diagnosticsWithParameterRenderers.kt
@@ -23,8 +23,8 @@ import java.text.MessageFormat
 abstract class AbstractDiagnosticWithParametersRenderer<D : Diagnostic> protected constructor(message: String) : DiagnosticRenderer<D> {
     private val messageFormat = MessageFormat(message)
 
-    override fun render(obj: D): String {
-        return messageFormat.format(renderParameters(obj))
+    override fun render(diagnostic: D): String {
+        return messageFormat.format(renderParameters(diagnostic))
     }
 
     abstract fun renderParameters(diagnostic: D): Array<out Any>
diff --git a/compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractFirDiagnosticTest.kt b/compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractFirDiagnosticTest.kt
index 5ee614c7114..9d71824715d 100644
--- a/compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractFirDiagnosticTest.kt
+++ b/compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractFirDiagnosticTest.kt
@@ -203,6 +203,7 @@ abstract class AbstractFirDiagnosticsTest : AbstractFirBaseDiagnosticsTest() {
         argument: () -> String,
     ): FirDiagnosticWithParameters1<FirSourceElement, String>? {
         val sourceElement = element.source ?: return null
+        if (sourceElement.kind != FirRealSourceElementKind) return null
         val name = name ?: return null
         if (diagnosedRangesToDiagnosticNames[sourceElement.startOffset..sourceElement.endOffset]?.contains(name) != true) return null