diff --git a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InitializersLowering.kt b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InitializersLowering.kt
index c4aee08c7a7..a128e6b2712 100644
--- a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InitializersLowering.kt
+++ b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InitializersLowering.kt
@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.backend.common.ir.SetDeclarationsParentVisitor
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.*
@@ -26,6 +27,7 @@ import org.jetbrains.kotlin.ir.util.patchDeclarationParents
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.ir.symbols.impl.IrSimpleFunctionSymbolImpl
+import org.jetbrains.kotlin.ir.visitors.*
 import org.jetbrains.kotlin.name.Name
 
 object SYNTHESIZED_INIT_BLOCK: IrStatementOriginImpl("SYNTHESIZED_INIT_BLOCK")
@@ -33,9 +35,22 @@ object SYNTHESIZED_INIT_BLOCK: IrStatementOriginImpl("SYNTHESIZED_INIT_BLOCK")
 fun makeInitializersPhase(origin: IrDeclarationOrigin, clinitNeeded: Boolean)= makeIrFilePhase(
     { context -> InitializersLowering(context, origin, clinitNeeded) },
     name = "Initializers",
-    description = "Handle initializer statements"
+    description = "Handle initializer statements",
+    stickyPostconditions = setOf(::checkNonAnonymousInitializers)
 )
 
+fun checkNonAnonymousInitializers(irFile: IrFile) {
+    irFile.acceptVoid(object : IrElementVisitorVoid {
+        override fun visitElement(element: IrElement) {
+            element.acceptChildrenVoid(this)
+        }
+
+        override fun visitAnonymousInitializer(declaration: IrAnonymousInitializer) {
+            error("No anonymous initializers should remain at this stage")
+        }
+    })
+}
+
 class InitializersLowering(
     val context: CommonBackendContext,
     val declarationOrigin: IrDeclarationOrigin,
@@ -48,6 +63,7 @@ class InitializersLowering(
         val staticInitializerStatements = handleStatics(irClass)
         if (clinitNeeded && staticInitializerStatements.isNotEmpty())
             createStaticInitializationMethod(irClass, staticInitializerStatements)
+        irClass.declarations.removeAll { it is IrAnonymousInitializer }
         irClass.patchDeclarationParents(irClass.parent)
     }
 
diff --git a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/PropertiesLowering.kt b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/PropertiesLowering.kt
index e5cb60c86d1..d39336512c3 100644
--- a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/PropertiesLowering.kt
+++ b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/PropertiesLowering.kt
@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFunctionImpl
@@ -23,15 +24,29 @@ import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.load.java.JvmAbi
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.ir.visitors.*
 import org.jetbrains.kotlin.utils.addIfNotNull
 import java.util.*
 
 fun makePropertiesPhase(originOfSyntheticMethodForAnnotations: IrDeclarationOrigin?) = makeIrFilePhase(
     { context -> PropertiesLowering(context, originOfSyntheticMethodForAnnotations) },
     name = "Properties",
-    description = "Move fields and accessors for properties to their classes"
+    description = "Move fields and accessors for properties to their classes",
+    stickyPostconditions = setOf(::checkNoProperties)
 )
 
+fun checkNoProperties(irFile: IrFile) {
+    irFile.acceptVoid(object : IrElementVisitorVoid {
+        override fun visitElement(element: IrElement) {
+            element.acceptChildrenVoid(this)
+        }
+
+        override fun visitProperty(declaration: IrProperty) {
+            error("No properties should remain at this stage")
+        }
+    })
+}
+
 class PropertiesLowering(
     private val context: BackendContext,
     private val originOfSyntheticMethodForAnnotations: IrDeclarationOrigin?
@@ -49,6 +64,7 @@ class PropertiesLowering(
     override fun visitClass(declaration: IrClass): IrStatement {
         declaration.transformChildrenVoid(this)
         declaration.transformDeclarationsFlat { lowerProperty(it, declaration.kind) }
+        declaration.declarations.removeAll { it is IrProperty }
         return declaration
     }
 
diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt
index 3ca40fa08db..96d8fe94703 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt
@@ -39,9 +39,14 @@ import java.util.*
 internal val fileClassPhase = makeIrFilePhase(
     ::FileClassLowering,
     name = "FileClass",
-    description = "Put file level function and property declaration into a class"
+    description = "Put file level function and property declaration into a class",
+    stickyPostconditions = setOf(::checkAllFileLevelDeclarationsAreClasses)
 )
 
+private fun checkAllFileLevelDeclarationsAreClasses(irFile: IrFile) {
+    assert(irFile.declarations.all { it is IrClass })
+}
+
 private class FileClassLowering(val context: JvmBackendContext) : FileLoweringPass {
     override fun lower(irFile: IrFile) {
         val classes = ArrayList<IrClass>()