diff --git a/dbms/src/Processors/Merges/IMergingTransform.h b/dbms/src/Processors/Merges/IMergingTransform.h
index 5680b92b6d3..58ad3a9b969 100644
--- a/dbms/src/Processors/Merges/IMergingTransform.h
+++ b/dbms/src/Processors/Merges/IMergingTransform.h
@@ -6,6 +6,11 @@
 namespace DB
 {
 
+namespace ErrorCodes
+{
+    extern const int LOGICAL_ERROR;
+}
+
 /// Base class for merging transforms.
 class IMergingTransform : public IProcessor
 {