diff --git a/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt b/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt
index ef70c0a200e..8abbcc9a365 100644
--- a/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt
+++ b/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt
@@ -21,8 +21,8 @@ open class KotlinExceptionWithAttachments : RuntimeException, ExceptionWithAttac
 
     override fun getAttachments(): Array<Attachment> = attachments.toTypedArray()
 
-    fun withAttachment(name: String, content: String?): KotlinExceptionWithAttachments {
-        attachments.add(Attachment(name, content ?: "<null>"))
+    fun withAttachment(name: String, content: Any?): KotlinExceptionWithAttachments {
+        attachments.add(Attachment(name, content?.toString() ?: "<null>"))
         return this
     }
 }
diff --git a/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt b/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt
index 4b03b8b4c72..1d5ec88c99d 100644
--- a/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt
+++ b/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt
@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.idea.completion
 import com.intellij.codeInsight.completion.CompletionParameters
 import com.intellij.psi.PsiElement
 import com.intellij.psi.util.PsiTreeUtil
+import org.jetbrains.kotlin.idea.util.application.runReadAction
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.utils.checkWithAttachment
@@ -34,16 +35,20 @@ class ToFromOriginalFileMapper private constructor(
     //TODO: lazy initialization?
 
     init {
-        val originalText = originalFile.text
-        val syntheticText = syntheticFile.text
+        val (originalText, syntheticText) = runReadAction {
+            originalFile.text to syntheticFile.text
+        }
         val originalSubSequence = originalText.take(completionOffset)
         val syntheticSubSequence = syntheticText.take(completionOffset)
         checkWithAttachment(originalSubSequence == syntheticSubSequence, {
             "original subText [len: ${originalSubSequence.length}]" +
-                    " does not match synthetic subText [len: ${syntheticSubSequence.length}]"
+                    " does not match synthetic subText [len: ${syntheticSubSequence.length}], " +
+                    "completionOffset: $completionOffset"
         }) {
-            it.withAttachment("original subText", originalSubSequence.toString())
-                .withAttachment("synthetic subText", syntheticSubSequence.toString())
+            it.withAttachment("original subText.kt", originalSubSequence)
+                .withAttachment("original.kt", originalText)
+                .withAttachment("synthetic subText.kt", syntheticSubSequence)
+                .withAttachment("synthetic.kt", syntheticText)
         }
 
         syntheticLength = syntheticText.length