diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt
index 65956ef94fc..2641f92d5d1 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt
@@ -43,8 +43,8 @@ import java.io.InputStream
 
 fun DeserializerForClassfileDecompiler(classFile: VirtualFile): DeserializerForClassfileDecompiler {
     val kotlinClassHeaderInfo = IDEKotlinBinaryClassCache.getKotlinBinaryClassHeaderData(classFile)
-    assert(kotlinClassHeaderInfo != null) { "Decompiled data factory shouldn't be called on an unsupported file: " + classFile }
-    val packageFqName = kotlinClassHeaderInfo!!.classId.packageFqName
+                                ?: error("Decompiled data factory shouldn't be called on an unsupported file: " + classFile)
+    val packageFqName = kotlinClassHeaderInfo.classId.packageFqName
     return DeserializerForClassfileDecompiler(classFile.parent!!, packageFqName)
 }