diff --git a/nj2k/src/org/jetbrains/kotlin/nj2k/tree/base.kt b/nj2k/src/org/jetbrains/kotlin/nj2k/tree/base.kt
index b213c069def..9c68d026f95 100644
--- a/nj2k/src/org/jetbrains/kotlin/nj2k/tree/base.kt
+++ b/nj2k/src/org/jetbrains/kotlin/nj2k/tree/base.kt
@@ -56,7 +56,9 @@ abstract class JKTreeElement : JKElement, JKFormattingOwner, Cloneable {
 
     override fun detach(from: JKElement) {
         val prevParent = parent
-        require(from == prevParent)
+        require(from == prevParent) {
+            "Incorrect detach: From: $from, Actual: $prevParent"
+        }
         parent = null
     }