diff --git a/src/database/sql/driver/types.go b/src/database/sql/driver/types.go
index 8b3cb6c..64b41fa 100644
--- a/src/database/sql/driver/types.go
+++ b/src/database/sql/driver/types.go
@@ -38,6 +38,7 @@
 // themselves to a driver Value.
 type Valuer interface {
 	// Value returns a driver Value.
+	// Value must not panic.
 	Value() (Value, error)
 }