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 b7297c0b0b4..b48bcc4dbf2 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
@@ -47,8 +47,8 @@ class ToFromOriginalFileMapper private constructor(
     init {
         val originalText = originalFile.text
         val syntheticText = syntheticFile.text
-        val originalSubSequence = originalText.subSequence(0, completionOffset)
-        val syntheticSubSequence = syntheticText.subSequence(0, completionOffset)
+        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}]"