diff --git a/compiler/frontend/serialization/src/org/jetbrains/jet/descriptors/serialization/DescriptorSerializer.java b/compiler/frontend/serialization/src/org/jetbrains/jet/descriptors/serialization/DescriptorSerializer.java
index 8a6eb2ea9c8..a845824dbb3 100644
--- a/compiler/frontend/serialization/src/org/jetbrains/jet/descriptors/serialization/DescriptorSerializer.java
+++ b/compiler/frontend/serialization/src/org/jetbrains/jet/descriptors/serialization/DescriptorSerializer.java
@@ -21,10 +21,7 @@ import com.google.common.base.Predicates;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.descriptors.annotations.Annotated;
-import org.jetbrains.jet.lang.types.JetType;
-import org.jetbrains.jet.lang.types.TypeConstructor;
-import org.jetbrains.jet.lang.types.TypeProjection;
-import org.jetbrains.jet.lang.types.Variance;
+import org.jetbrains.jet.lang.types.*;
 import org.jetbrains.jet.renderer.DescriptorRenderer;
 
 import java.util.*;
@@ -238,6 +235,8 @@ public class DescriptorSerializer {
 
     @NotNull
     public ProtoBuf.Type.Builder type(@NotNull JetType type) {
+        assert !ErrorUtils.isErrorType(type) : "Can't serialize error types: " + type; // TODO
+
         ProtoBuf.Type.Builder builder = ProtoBuf.Type.newBuilder();
 
         builder.setConstructor(typeConstructor(type.getConstructor()));