diff --git a/ast/misc.go b/ast/misc.go
index 1fc870c17..58fc6ee94 100755
--- a/ast/misc.go
+++ b/ast/misc.go
@@ -63,11 +63,12 @@ const (
 	RepeatableRead  = "REPEATABLE-READ"
 
 	// Valid formats for explain statement.
-	ExplainFormatROW  = "row"
-	ExplainFormatDOT  = "dot"
-	ExplainFormatHint = "hint"
-	PumpType          = "PUMP"
-	DrainerType       = "DRAINER"
+	ExplainFormatROW   = "row"
+	ExplainFormatDOT   = "dot"
+	ExplainFormatHint  = "hint"
+	ExplainFormatTrace = "opt_trace"
+	PumpType           = "PUMP"
+	DrainerType        = "DRAINER"
 )
 
 // Transaction mode constants.