diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt
index a8797e14fc8..c6d49b817fd 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt
@@ -704,7 +704,7 @@ private fun findDefaultValue(source: KtLightSourceElement): KtLightSourceElement
 
 fun ConeKotlinType.getInlineClassUnderlyingType(session: FirSession): ConeKotlinType {
     require(this.isSingleFieldValueClass(session))
-    return toRegularClassSymbol(session)!!.primaryConstructorSymbol()!!.valueParameterSymbols[0].resolvedReturnTypeRef.coneType
+    return toRegularClassSymbol(session)!!.primaryConstructorSymbol(session)!!.valueParameterSymbols[0].resolvedReturnTypeRef.coneType
 }
 
 fun FirNamedFunctionSymbol.directOverriddenFunctions(session: FirSession, scopeSession: ScopeSession): List<FirNamedFunctionSymbol> {
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirAnnotationClassDeclarationChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirAnnotationClassDeclarationChecker.kt
index 9692477c4e8..4ef5e6dad0f 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirAnnotationClassDeclarationChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirAnnotationClassDeclarationChecker.kt
@@ -168,7 +168,7 @@ object FirAnnotationClassDeclarationChecker : FirRegularClassChecker() {
     }
 
     private fun checkCyclesInParameters(annotation: FirRegularClassSymbol, context: CheckerContext, reporter: DiagnosticReporter) {
-        val primaryConstructor = annotation.primaryConstructorSymbol() ?: return
+        val primaryConstructor = annotation.primaryConstructorSymbol(context.session) ?: return
         val checker = CycleChecker(annotation, context.session)
         for (valueParameter in primaryConstructor.valueParameterSymbols) {
             if (checker.parameterHasCycle(annotation, valueParameter)) {
@@ -182,7 +182,7 @@ object FirAnnotationClassDeclarationChecker : FirRegularClassChecker() {
         private val annotationsWithCycle = mutableSetOf(targetAnnotation)
 
         fun annotationHasCycle(annotation: FirRegularClassSymbol): Boolean {
-            val primaryConstructor = annotation.primaryConstructorSymbol() ?: return false
+            val primaryConstructor = annotation.primaryConstructorSymbol(session) ?: return false
             for (valueParameter in primaryConstructor.valueParameterSymbols) {
                 if (parameterHasCycle(annotation, valueParameter)) return true
             }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/declarationUtils.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/declarationUtils.kt
index 7a5250a9009..3dc67b99e51 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/declarationUtils.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/declarationUtils.kt
@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.fir.analysis.checkers.modality
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.utils.*
 import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
+import org.jetbrains.kotlin.fir.symbols.SymbolInternals
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.fir.types.coneType
@@ -96,13 +97,9 @@ internal val FirBasedSymbol<*>.isLocalMember: Boolean
 internal val FirCallableSymbol<*>.isExtensionMember: Boolean
     get() = resolvedReceiverTypeRef != null && dispatchReceiverType != null
 
-fun FirClassSymbol<*>.primaryConstructorSymbol(): FirConstructorSymbol? {
-    for (declarationSymbol in this.declarationSymbols) {
-        if (declarationSymbol is FirConstructorSymbol && declarationSymbol.isPrimary) {
-            return declarationSymbol
-        }
-    }
-    return null
+@OptIn(SymbolInternals::class)
+fun FirClassSymbol<*>.primaryConstructorSymbol(session: FirSession): FirConstructorSymbol? {
+    return fir.primaryConstructorIfAny(session)
 }
 
 fun FirTypeRef.needsMultiFieldValueClassFlattening(session: FirSession) = with(session.typeContext) {
diff --git a/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/services/FirSerializablePropertiesProvider.kt b/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/services/FirSerializablePropertiesProvider.kt
index 0fdb6314644..da70ee0be0a 100644
--- a/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/services/FirSerializablePropertiesProvider.kt
+++ b/plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/services/FirSerializablePropertiesProvider.kt
@@ -89,7 +89,7 @@ class FirSerializablePropertiesProvider(session: FirSession) : FirExtensionSessi
             .let { restoreCorrectOrderFromClassProtoExtension(classSymbol, it) }
 
         val isExternallySerializable = classSymbol.isEnumClass ||
-                primaryConstructorProperties.size == (classSymbol.primaryConstructorSymbol()?.valueParameterSymbols?.size ?: 0)
+                primaryConstructorProperties.size == (classSymbol.primaryConstructorSymbol(session)?.valueParameterSymbols?.size ?: 0)
 
         val (serializableConstructorProperties, serializableStandaloneProperties) = serializableProperties.partition { it.propertySymbol in primaryConstructorProperties }
         return FirSerializableProperties(