diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt
index 7930cdd12f5..9c654dca277 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt
@@ -9,7 +9,6 @@ import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.analysis.checkersComponent
 import org.jetbrains.kotlin.fir.analysis.extensions.additionalCheckers
 import org.jetbrains.kotlin.fir.extensions.extensionService
-import org.jetbrains.kotlin.fir.extensions.oldExtensionsService
 
 object FirDiagnosticsCollector {
     fun create(session: FirSession): AbstractDiagnosticCollector {
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/extensions/FirOldExtensionsService.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/extensions/FirOldExtensionsService.kt
deleted file mode 100644
index cd5e979265d..00000000000
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/extensions/FirOldExtensionsService.kt
+++ /dev/null
@@ -1,178 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir.extensions
-
-import com.google.common.collect.LinkedHashMultimap
-import com.google.common.collect.Multimap
-import org.jetbrains.kotlin.fir.FirAnnotationContainer
-import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.FirSessionComponent
-import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
-import org.jetbrains.kotlin.fir.declarations.FirPluginKey
-import org.jetbrains.kotlin.fir.declarations.FirRegularClass
-import org.jetbrains.kotlin.fir.resolve.fqName
-import org.jetbrains.kotlin.fir.utils.ComponentArrayOwner
-import org.jetbrains.kotlin.fir.utils.TypeRegistry
-import kotlin.properties.ReadOnlyProperty
-import kotlin.reflect.KClass
-import kotlin.reflect.KProperty
-
-class OldFirRegisteredExtension<P : FirExtension>(
-    val extensionsWithAllMode: List<P>,
-    val extensionsWithAnnotatedMode: Multimap<AnnotationFqn, P>,
-    val extensionsWithAllInAnnotatedMode: Multimap<AnnotationFqn, P>,
-    val extensionsByPluginKey: Multimap<FirPluginKey, P>
-) {
-    fun isEmpty(): Boolean {
-        return extensionsWithAllMode.isEmpty() && extensionsWithAnnotatedMode.isEmpty() && extensionsWithAllInAnnotatedMode.isEmpty()
-    }
-}
-
-@Deprecated("")
-class FirOldExtensionsService(
-    val session: FirSession
-) : ComponentArrayOwner<FirExtension, OldFirRegisteredExtension<*>>(), FirSessionComponent {
-    companion object : TypeRegistry<FirExtension, OldFirRegisteredExtension<*>>() {
-        inline fun <reified P : FirExtension, V : OldFirRegisteredExtension<P>> registeredExtensions(): ReadOnlyProperty<FirOldExtensionsService, ExtensionsAccessor<P>> {
-            val accessor = generateAccessor<V, P>(P::class)
-            return object : ReadOnlyProperty<FirOldExtensionsService, ExtensionsAccessor<P>> {
-                override fun getValue(thisRef: FirOldExtensionsService, property: KProperty<*>): ExtensionsAccessor<P> {
-                    return ExtensionsAccessor(thisRef.session, accessor.getValue(thisRef, property))
-                }
-            }
-        }
-
-        private fun <K, V> createMultimap(): Multimap<K, V> = LinkedHashMultimap.create()
-    }
-
-    override val typeRegistry: TypeRegistry<FirExtension, OldFirRegisteredExtension<*>>
-        get() = Companion
-
-    fun <P : FirExtension> registerExtensions(extensionClass: KClass<P>, extensionFactories: List<FirExtension.Factory<P>>) {
-//        registeredExtensionsSize += extensionFactories.size
-//        val extensions = extensionFactories.map { it.create(session) }
-//
-//        val extensionsWithAllMode = mutableListOf<P>()
-//        val extensionsWithAnnotatedMode = createMultimap<AnnotationFqn, P>()
-//        val extensionsWithAllInAnnotatedMode = createMultimap<AnnotationFqn, P>()
-//        val extensionsByPlugin = createMultimap<FirPluginKey, P>()
-//        for (extension in extensions) {
-//            _metaAnnotations += extension.metaAnnotations.keys
-//            for (metaAnnotation in extension.metaAnnotations.keys) {
-//                extensionsWithMetaAnnotations.put(metaAnnotation, extension)
-//            }
-//            _annotations += extension.directlyApplicableAnnotations
-//            _annotations += extension.childrenApplicableAnnotations
-//            when (extension.mode) {
-//                FirExtension.Mode.ANNOTATED_ELEMENT -> {
-//                    for (annotation in extension.directlyApplicableAnnotations) {
-//                        extensionsWithAnnotatedMode.put(annotation, extension)
-//                    }
-//                    for (annotation in extension.childrenApplicableAnnotations) {
-//                        extensionsWithAllInAnnotatedMode.put(annotation, extension)
-//                    }
-//                }
-//                FirExtension.Mode.ALL -> extensionsWithAllMode += extension
-//            }
-//            extensionsByPlugin.put(extension.key, extension)
-//        }
-//        registerComponent(
-//            extensionClass,
-//            FirRegisteredExtension(
-//                extensionsWithAllMode,
-//                extensionsWithAnnotatedMode,
-//                extensionsWithAllInAnnotatedMode,
-//                extensionsByPlugin
-//            )
-//        )
-    }
-
-    @Deprecated("")
-    fun registerUserDefinedAnnotation(metaAnnotation: AnnotationFqn, annotations: Collection<FirRegularClass>) {
-//        for (annotation in annotations) {
-//            require(annotation.classKind == ClassKind.ANNOTATION_CLASS)
-//            val fqName = annotation.symbol.classId.asSingleFqName()
-//            _annotations += fqName
-//            userDefinedAnnotations.put(metaAnnotation, fqName)
-//            val extensions = extensionsWithMetaAnnotations[metaAnnotation]
-//            if (extensions.isEmpty()) return
-//            for (extension in extensions) {
-//                val registeredExtensions = this[extension.extensionType]
-//
-//                val metaAnnotationMode = extension.metaAnnotations.getValue(metaAnnotation)
-//
-//                if (metaAnnotationMode.directed) {
-//                    @Suppress("UNCHECKED_CAST")
-//                    (registeredExtensions.extensionsWithAnnotatedMode as Multimap<AnnotationFqn, FirExtension>).put(fqName, extension)
-//                }
-//
-//                if (metaAnnotationMode.children) {
-//                    @Suppress("UNCHECKED_CAST")
-//                    (registeredExtensions.extensionsWithAllInAnnotatedMode as Multimap<AnnotationFqn, FirExtension>).put(fqName, extension)
-//                }
-//            }
-//        }
-    }
-
-    @Deprecated("")
-    val annotations: Set<AnnotationFqn>
-        get() = _annotations
-    private val _annotations: MutableSet<AnnotationFqn> = mutableSetOf()
-
-    @Deprecated("")
-    val metaAnnotations: Set<AnnotationFqn>
-        get() = _metaAnnotations
-    private val _metaAnnotations: MutableSet<AnnotationFqn> = mutableSetOf()
-
-    private val extensionsWithMetaAnnotations: Multimap<AnnotationFqn, FirExtension> = createMultimap()
-
-    // MetaAnnotation -> Annotations
-    @Deprecated("")
-    val userDefinedAnnotations: Multimap<AnnotationFqn, AnnotationFqn> = createMultimap()
-
-    var registeredExtensionsSize: Int = 0
-        private set
-
-    class ExtensionsAccessor<P : FirExtension>(
-        private val session: FirSession,
-        private val extensions: OldFirRegisteredExtension<P>
-    ) {
-        fun forDeclaration(declaration: FirAnnotationContainer, owners: Collection<FirAnnotationContainer>): Collection<P> {
-            if (extensions.isEmpty()) return emptySet()
-            if (
-                (declaration.annotations.isEmpty() || extensions.extensionsWithAnnotatedMode.isEmpty) &&
-                extensions.extensionsWithAllInAnnotatedMode.isEmpty
-            ) {
-                return extensions.extensionsWithAllMode
-            }
-
-            return LinkedHashSet(extensions.extensionsWithAllMode).apply {
-                collectExtensions(this, declaration, extensions.extensionsWithAnnotatedMode)
-                collectExtensions(this, declaration, extensions.extensionsWithAllInAnnotatedMode)
-                for (owner in owners) {
-                    collectExtensions(this, owner, extensions.extensionsWithAllInAnnotatedMode)
-                }
-            }
-        }
-
-        fun forGeneratedDeclaration(origin: FirDeclarationOrigin.Plugin): Collection<P> {
-            return extensions.extensionsByPluginKey.get(origin.key)
-        }
-
-        private fun collectExtensions(result: MutableSet<P>, declaration: FirAnnotationContainer, extensions: Multimap<AnnotationFqn, P>) {
-            for (annotation in declaration.annotations) {
-                val fqName = annotation.fqName(session) ?: continue
-                result += extensions[fqName]
-            }
-        }
-    }
-}
-
-@Deprecated("")
-val FirSession.oldExtensionsService: FirOldExtensionsService by FirSession.sessionComponentAccessor()
-
-val FirOldExtensionsService.hasExtensions: Boolean
-    get() = registeredExtensionsSize > 0
\ No newline at end of file
diff --git a/idea/idea-fir/tests/org/jetbrains/kotlin/idea/fir/AbstractFirMultiModuleResolveTest.kt b/idea/idea-fir/tests/org/jetbrains/kotlin/idea/fir/AbstractFirMultiModuleResolveTest.kt
index 47835ff02a1..ebb88b8b517 100644
--- a/idea/idea-fir/tests/org/jetbrains/kotlin/idea/fir/AbstractFirMultiModuleResolveTest.kt
+++ b/idea/idea-fir/tests/org/jetbrains/kotlin/idea/fir/AbstractFirMultiModuleResolveTest.kt
@@ -17,7 +17,9 @@ import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
 import org.jetbrains.kotlin.fir.dependenciesWithoutSelf
 import org.jetbrains.kotlin.fir.extensions.FirExtensionRegistrar
+import org.jetbrains.kotlin.fir.extensions.extensionService
 import org.jetbrains.kotlin.fir.extensions.oldExtensionsService
+import org.jetbrains.kotlin.fir.extensions.registerExtensions
 import org.jetbrains.kotlin.fir.java.FirJavaModuleBasedSession
 import org.jetbrains.kotlin.fir.java.FirLibrarySession
 import org.jetbrains.kotlin.fir.java.FirProjectSessionProvider
@@ -71,7 +73,7 @@ abstract class AbstractFirMultiModuleResolveTest : AbstractMultiModuleTest() {
     private fun createSession(module: Module, provider: FirProjectSessionProvider): FirJavaModuleBasedSession {
         val moduleInfo = module.productionSourceInfo()!!
         return FirJavaModuleBasedSession(moduleInfo, provider, moduleInfo.contentScope()).also {
-            it.oldExtensionsService.registerExtensions(FirExtensionRegistrar.OldRegisteredExtensions.EMPTY)
+            it.extensionService.registerExtensions(emptyList())
         }
     }