diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IDELightClassGenerationSupport.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IDELightClassGenerationSupport.kt
index 97f6daff8b2..35809f00c4e 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IDELightClassGenerationSupport.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IDELightClassGenerationSupport.kt
@@ -43,6 +43,7 @@ import org.jetbrains.kotlin.idea.caches.lightClasses.LazyLightClassDataHolder
 import org.jetbrains.kotlin.idea.project.languageVersionSettings
 import org.jetbrains.kotlin.idea.resolve.frontendService
 import org.jetbrains.kotlin.idea.stubindex.KotlinTypeAliasShortNameIndex
+import org.jetbrains.kotlin.idea.util.application.runReadAction
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
@@ -139,25 +140,27 @@ class IDELightClassGenerationSupport(private val project: Project) : LightClassG
     }
 
     override fun createUltraLightClass(element: KtClassOrObject): KtUltraLightClass? {
-        if (element.shouldNotBeVisibleAsLightClass() ||
-            element is KtEnumEntry ||
-            element.containingKtFile.isScript()
-        ) {
-            return null
-        }
+        return runReadAction {
+            if (element.shouldNotBeVisibleAsLightClass() ||
+                element is KtEnumEntry ||
+                element.containingKtFile.isScript()
+            ) {
+                return@runReadAction null
+            }
 
-        return KtUltraLightSupportImpl(element).let { support ->
-            when {
-                element is KtObjectDeclaration && element.isObjectLiteral() ->
-                    KtUltraLightClassForAnonymousDeclaration(element, support)
+            KtUltraLightSupportImpl(element).let { support ->
+                when {
+                    element is KtObjectDeclaration && element.isObjectLiteral() ->
+                        KtUltraLightClassForAnonymousDeclaration(element, support)
 
-                element.isLocal ->
-                    KtUltraLightClassForLocalDeclaration(element, support)
+                    element.isLocal ->
+                        KtUltraLightClassForLocalDeclaration(element, support)
 
-                (element.hasModifier(KtTokens.INLINE_KEYWORD)) ->
-                    KtUltraLightInlineClass(element, support)
+                    (element.hasModifier(KtTokens.INLINE_KEYWORD)) ->
+                        KtUltraLightInlineClass(element, support)
 
-                else -> KtUltraLightClass(element, support)
+                    else -> KtUltraLightClass(element, support)
+                }
             }
         }
     }