diff --git a/src/cmd/internal/gc/esc.go b/src/cmd/internal/gc/esc.go
index 40125888ca..76ce87d513 100644
--- a/src/cmd/internal/gc/esc.go
+++ b/src/cmd/internal/gc/esc.go
@@ -231,6 +231,7 @@ type EscState struct {
 
 var tags [16]*string
 
+// mktag returns the string representation for an escape analysis tag.
 func mktag(mask int) *string {
 	switch mask & EscMask {
 	case EscNone,