diff --git a/go/gcimporter15/bexport.go b/go/gcimporter15/bexport.go
index 1ceae137..9ff0d771 100644
--- a/go/gcimporter15/bexport.go
+++ b/go/gcimporter15/bexport.go
@@ -42,6 +42,17 @@ const trace = false // default: false
 
 const exportVersion = "v0"
 
+// trackAllTypes enables cycle tracking for all types, not just named
+// types. The existing compiler invariants assume that unnamed types
+// that are not completely set up are not used, or else there are spurious
+// errors.
+// If disabled, only named types are tracked, possibly leading to slightly
+// less efficient encoding in rare cases. It also prevents the export of
+// some corner-case type declarations (but those are not handled correctly
+// with with the textual export format either).
+// TODO(gri) enable and remove once issues caused by it are fixed
+const trackAllTypes = false
+
 type exporter struct {
 	fset *token.FileSet
 	out  bytes.Buffer
@@ -79,6 +90,12 @@ func BExportData(fset *token.FileSet, pkg *types.Package) []byte {
 	}
 	p.rawByte(format)
 
+	format = 'n' // track named types only
+	if trackAllTypes {
+		format = 'a'
+	}
+	p.rawByte(format)
+
 	// posInfo exported or not?
 	p.bool(p.posInfoFormat)
 
@@ -283,15 +300,21 @@ func (p *exporter) typ(t types.Type) {
 	}
 
 	// otherwise, remember the type, write the type tag (< 0) and type data
-	index := len(p.typIndex)
-	if trace {
-		p.tracef("T%d = {>\n", index)
-		defer p.tracef("<\n} ")
+	if trackAllTypes {
+		if trace {
+			p.tracef("T%d = {>\n", len(p.typIndex))
+			defer p.tracef("<\n} ")
+		}
+		p.typIndex[t] = len(p.typIndex)
 	}
-	p.typIndex[t] = index
 
 	switch t := t.(type) {
 	case *types.Named:
+		if !trackAllTypes {
+			// if we don't track all types, track named types now
+			p.typIndex[t] = len(p.typIndex)
+		}
+
 		p.tag(namedTag)
 		p.pos(t.Obj())
 		p.qualifiedName(t.Obj())
diff --git a/go/gcimporter15/bimport.go b/go/gcimporter15/bimport.go
index e6b4863e..f3fe519e 100644
--- a/go/gcimporter15/bimport.go
+++ b/go/gcimporter15/bimport.go
@@ -28,9 +28,10 @@ type importer struct {
 	buf     []byte // for reading strings
 
 	// object lists
-	strList []string         // in order of appearance
-	pkgList []*types.Package // in order of appearance
-	typList []types.Type     // in order of appearance
+	strList       []string         // in order of appearance
+	pkgList       []*types.Package // in order of appearance
+	typList       []types.Type     // in order of appearance
+	trackAllTypes bool
 
 	// position encoding
 	posInfoFormat bool
@@ -68,6 +69,8 @@ func BImportData(fset *token.FileSet, imports map[string]*types.Package, data []
 		return p.read, nil, fmt.Errorf("invalid encoding format in export data: got %q; want 'c' or 'd'", format)
 	}
 
+	p.trackAllTypes = p.rawByte() == 'a'
+
 	p.posInfoFormat = p.int() != 0
 
 	// --- generic export data ---
@@ -102,7 +105,12 @@ func BImportData(fset *token.FileSet, imports map[string]*types.Package, data []
 
 	// complete interfaces
 	for _, typ := range p.typList {
-		if it, ok := typ.(*types.Interface); ok {
+		// If we only record named types (!p.trackAllTypes),
+		// we must check the underlying types here. If we
+		// track all types, the Underlying() method call is
+		// not needed.
+		// TODO(gri) Remove if p.trackAllTypes is gone.
+		if it, ok := typ.Underlying().(*types.Interface); ok {
 			it.Complete()
 		}
 	}
@@ -344,7 +352,9 @@ func (p *importer) typ(parent *types.Package) types.Type {
 
 	case arrayTag:
 		t := new(types.Array)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		n := p.int64()
 		*t = *types.NewArray(p.typ(parent), n)
@@ -352,35 +362,45 @@ func (p *importer) typ(parent *types.Package) types.Type {
 
 	case sliceTag:
 		t := new(types.Slice)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		*t = *types.NewSlice(p.typ(parent))
 		return t
 
 	case dddTag:
 		t := new(dddSlice)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		t.elem = p.typ(parent)
 		return t
 
 	case structTag:
 		t := new(types.Struct)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		*t = *types.NewStruct(p.fieldList(parent))
 		return t
 
 	case pointerTag:
 		t := new(types.Pointer)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		*t = *types.NewPointer(p.typ(parent))
 		return t
 
 	case signatureTag:
 		t := new(types.Signature)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		params, isddd := p.paramList()
 		result, _ := p.paramList()
@@ -393,7 +413,9 @@ func (p *importer) typ(parent *types.Package) types.Type {
 		// such cycle must contain a named type which would have been
 		// first defined earlier.
 		n := len(p.typList)
-		p.record(nil)
+		if p.trackAllTypes {
+			p.record(nil)
+		}
 
 		// no embedded interfaces with gc compiler
 		if p.int() != 0 {
@@ -401,12 +423,16 @@ func (p *importer) typ(parent *types.Package) types.Type {
 		}
 
 		t := types.NewInterface(p.methodList(parent), nil)
-		p.typList[n] = t
+		if p.trackAllTypes {
+			p.typList[n] = t
+		}
 		return t
 
 	case mapTag:
 		t := new(types.Map)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		key := p.typ(parent)
 		val := p.typ(parent)
@@ -415,7 +441,9 @@ func (p *importer) typ(parent *types.Package) types.Type {
 
 	case chanTag:
 		t := new(types.Chan)
-		p.record(t)
+		if p.trackAllTypes {
+			p.record(t)
+		}
 
 		var dir types.ChanDir
 		// tag values must match the constants in cmd/compile/internal/gc/go.go