diff --git a/src/runtime/debug/mod.go b/src/runtime/debug/mod.go
index b0dbe158c4..8b7a42305e 100644
--- a/src/runtime/debug/mod.go
+++ b/src/runtime/debug/mod.go
@@ -47,7 +47,7 @@ type BuildInfo struct {
 	// (for example, "golang.org/x/tools/cmd/stringer").
 	Path string
 
-	// Main describes the module that contains the main package for the binary
+	// Main describes the module that contains the main package for the binary.
 	Main Module
 
 	// Deps describes all the dependency modules, both direct and indirect,