diff --git a/godoc/godoc.go b/godoc/godoc.go
index 86575f60f7..0681a5adb7 100644
--- a/godoc/godoc.go
+++ b/godoc/godoc.go
@@ -33,7 +33,9 @@ import (
 )
 
 // Fake relative package path for built-ins. Documentation for all globals
-// (not just exported ones) will be shown for packages in this directory.
+// (not just exported ones) will be shown for packages in this directory,
+// and there will be no association of consts, vars, and factory functions
+// with types (see issue 6645).
 const builtinPkgPath = "builtin"
 
 // FuncMap defines template functions used in godoc templates.
diff --git a/godoc/server.go b/godoc/server.go
index b03e14a6e9..693599b4dc 100644
--- a/godoc/server.go
+++ b/godoc/server.go
@@ -268,7 +268,10 @@ func (h *handlerServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	abspath := pathpkg.Join(h.fsRoot, relpath)
 	mode := h.p.GetPageInfoMode(r)
 	if relpath == builtinPkgPath {
-		mode = NoFiltering | NoTypeAssoc
+		// The fake built-in package contains unexported identifiers,
+		// but we want to show them. Also, disable type association,
+		// since it's not helpful for this fake package (see issue 6645).
+		mode |= NoFiltering | NoTypeAssoc
 	}
 	info := h.GetPageInfo(abspath, relpath, mode, r.FormValue("GOOS"), r.FormValue("GOARCH"))
 	if info.Err != nil {
@@ -357,7 +360,7 @@ const (
 	AllMethods                           // show all embedded methods
 	ShowSource                           // show source code, do not extract documentation
 	FlatDir                              // show directory in a flat (non-indented) manner
-	NoTypeAssoc                          // don't associate consts, vars, and factory functions with types
+	NoTypeAssoc                          // don't associate consts, vars, and factory functions with types (not exposed via ?m= query parameter, used for package builtin, see issue 6645)
 )
 
 // modeNames defines names for each PageInfoMode flag.