diff --git a/src/net/http/header.go b/src/net/http/header.go
index 6437f2d2c07..e0b342c63cb 100644
--- a/src/net/http/header.go
+++ b/src/net/http/header.go
@@ -43,7 +43,8 @@ func (h Header) Set(key, value string) {
 // Get gets the first value associated with the given key. If
 // there are no values associated with the key, Get returns "".
 // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
-// used to canonicalize the provided key. To use non-canonical keys,
+// used to canonicalize the provided key. Get assumes that all
+// keys are stored in canonical form. To use non-canonical keys,
 // access the map directly.
 func (h Header) Get(key string) string {
 	return textproto.MIMEHeader(h).Get(key)