diff --git a/src/cmd/compile/internal/gc/universe.go b/src/cmd/compile/internal/gc/universe.go
index 745ce66bba2..104c6bab23d 100644
--- a/src/cmd/compile/internal/gc/universe.go
+++ b/src/cmd/compile/internal/gc/universe.go
@@ -386,6 +386,7 @@ func lexinit1() {
 	types.Errortype.Sym = s
 	types.Errortype.Orig = makeErrorInterface()
 	s.Def = asTypesNode(typenod(types.Errortype))
+	dowidth(types.Errortype)
 
 	// We create separate byte and rune types for better error messages
 	// rather than just creating type alias *types.Sym's for the uint8 and
@@ -401,6 +402,7 @@ func lexinit1() {
 	types.Bytetype.Sym = s
 	s.Def = asTypesNode(typenod(types.Bytetype))
 	asNode(s.Def).Name = new(Name)
+	dowidth(types.Bytetype)
 
 	// rune alias
 	s = builtinpkg.Lookup("rune")
@@ -408,6 +410,7 @@ func lexinit1() {
 	types.Runetype.Sym = s
 	s.Def = asTypesNode(typenod(types.Runetype))
 	asNode(s.Def).Name = new(Name)
+	dowidth(types.Runetype)
 
 	// backend-dependent builtin types (e.g. int).
 	for _, s := range typedefs {
diff --git a/test/fixedbugs/issue29350.go b/test/fixedbugs/issue29350.go
new file mode 100644
index 00000000000..9d59f6f6c0f
--- /dev/null
+++ b/test/fixedbugs/issue29350.go
@@ -0,0 +1,9 @@
+// compile
+
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var X interface{} = 'x'