diff --git a/api/go1.15.txt b/api/go1.15.txt
index f16faa07..b51837c 100644
--- a/api/go1.15.txt
+++ b/api/go1.15.txt
@@ -114,7 +114,6 @@
 pkg debug/pe, const IMAGE_SUBSYSTEM_XBOX ideal-int
 pkg go/printer, const StdFormat = 16
 pkg go/printer, const StdFormat Mode
-pkg go/types, type Config struct, UsesCgo bool
 pkg math/big, method (*Int) FillBytes([]uint8) []uint8
 pkg net, method (*Resolver) LookupIP(context.Context, string, string) ([]IP, error)
 pkg net/url, method (*URL) EscapedFragment() string
diff --git a/src/go/internal/srcimporter/srcimporter.go b/src/go/internal/srcimporter/srcimporter.go
index daef27c..90bb3a9 100644
--- a/src/go/internal/srcimporter/srcimporter.go
+++ b/src/go/internal/srcimporter/srcimporter.go
@@ -20,6 +20,7 @@
 	"path/filepath"
 	"strings"
 	"sync"
+	_ "unsafe" // for go:linkname
 )
 
 // An Importer provides the context for importing packages from source code.
@@ -133,7 +134,7 @@
 			// build.Context's VFS.
 			conf.FakeImportC = true
 		} else {
-			conf.UsesCgo = true
+			setUsesCgo(&conf)
 			file, err := p.cgo(bp)
 			if err != nil {
 				return nil, err
@@ -260,3 +261,6 @@
 	}
 	return filepath.Join(elem...)
 }
+
+//go:linkname setUsesCgo go/types.srcimporter_setUsesCgo
+func setUsesCgo(conf *types.Config)
diff --git a/src/go/types/api.go b/src/go/types/api.go
index 7787b88..1abcd9d 100644
--- a/src/go/types/api.go
+++ b/src/go/types/api.go
@@ -105,14 +105,14 @@
 	//          Do not use casually!
 	FakeImportC bool
 
-	// If UsesCgo is set, the type checker expects the
+	// If go115UsesCgo is set, the type checker expects the
 	// _cgo_gotypes.go file generated by running cmd/cgo to be
 	// provided as a package source file. Qualified identifiers
 	// referring to package C will be resolved to cgo-provided
 	// declarations within _cgo_gotypes.go.
 	//
-	// It is an error to set both FakeImportC and UsesCgo.
-	UsesCgo bool
+	// It is an error to set both FakeImportC and go115UsesCgo.
+	go115UsesCgo bool
 
 	// If Error != nil, it is called with each error found
 	// during type checking; err has dynamic type Error.
@@ -140,6 +140,10 @@
 	DisableUnusedImportCheck bool
 }
 
+func srcimporter_setUsesCgo(conf *Config) {
+	conf.go115UsesCgo = true
+}
+
 // Info holds result type information for a type-checked package.
 // Only the information for which a map is provided is collected.
 // If the package has type errors, the collected information may
diff --git a/src/go/types/check.go b/src/go/types/check.go
index a94770f..007babd 100644
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -248,10 +248,10 @@
 // Files checks the provided files as part of the checker's package.
 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
 
-var errBadCgo = errors.New("cannot use FakeImportC and UsesCgo together")
+var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
 
 func (check *Checker) checkFiles(files []*ast.File) (err error) {
-	if check.conf.FakeImportC && check.conf.UsesCgo {
+	if check.conf.FakeImportC && check.conf.go115UsesCgo {
 		return errBadCgo
 	}
 
diff --git a/src/go/types/resolver.go b/src/go/types/resolver.go
index f80b4ec..078adc5 100644
--- a/src/go/types/resolver.go
+++ b/src/go/types/resolver.go
@@ -141,10 +141,10 @@
 	}
 
 	// no package yet => import it
-	if path == "C" && (check.conf.FakeImportC || check.conf.UsesCgo) {
+	if path == "C" && (check.conf.FakeImportC || check.conf.go115UsesCgo) {
 		imp = NewPackage("C", "C")
 		imp.fake = true // package scope is not populated
-		imp.cgo = check.conf.UsesCgo
+		imp.cgo = check.conf.go115UsesCgo
 	} else {
 		// ordinary import
 		var err error