diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/state/BuilderfactoryForDuplicateSignatureDiagnostics.kt b/compiler/backend/src/org/jetbrains/jet/codegen/state/BuilderFactoryForDuplicateSignatureDiagnostics.kt
similarity index 97%
rename from compiler/backend/src/org/jetbrains/jet/codegen/state/BuilderfactoryForDuplicateSignatureDiagnostics.kt
rename to compiler/backend/src/org/jetbrains/jet/codegen/state/BuilderFactoryForDuplicateSignatureDiagnostics.kt
index 935ab599a2f..0c2512666e7 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/state/BuilderfactoryForDuplicateSignatureDiagnostics.kt
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/state/BuilderFactoryForDuplicateSignatureDiagnostics.kt
@@ -34,11 +34,13 @@ import org.jetbrains.jet.lang.resolve.java.descriptor.SamAdapterDescriptor
 
 class BuilderFactoryForDuplicateSignatureDiagnostics(
         builderFactory: ClassBuilderFactory,
-        private val typeMapper: JetTypeMapper,
         private val bindingContext: BindingContext,
         private val diagnostics: DiagnosticHolder
 ) : SignatureCollectingClassBuilderFactory(builderFactory) {
 
+    // Avoid errors when some classes are not loaded for some reason
+    private val typeMapper = JetTypeMapper(bindingContext, ClassBuilderMode.LIGHT_CLASSES)
+
     override fun handleClashingSignatures(data: ConflictingJvmDeclarationsData) {
         val allDelegatedToTraitImpls = data.signatureOrigins.all { it.originKind == JvmDeclarationOriginKind.DELEGATION_TO_TRAIT_IMPL }
 
diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/state/GenerationState.java b/compiler/backend/src/org/jetbrains/jet/codegen/state/GenerationState.java
index 0e2c2ab9add..ae7bedf5c3d 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/state/GenerationState.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/state/GenerationState.java
@@ -146,7 +146,7 @@ public class GenerationState {
 
         this.intrinsics = new IntrinsicMethods();
         this.classFileFactory = new ClassFileFactory(this, new BuilderFactoryForDuplicateSignatureDiagnostics(
-                builderFactory, typeMapper, bindingContext, diagnostics));
+                builderFactory, this.bindingContext, diagnostics));
 
         this.generateNotNullAssertions = generateNotNullAssertions;
         this.generateNotNullParamAssertions = generateNotNullParamAssertions;