diff --git a/src/cmd/compile/internal/noder/expr.go b/src/cmd/compile/internal/noder/expr.go
index a1160d42c4..54b07c39f4 100644
--- a/src/cmd/compile/internal/noder/expr.go
+++ b/src/cmd/compile/internal/noder/expr.go
@@ -6,7 +6,6 @@ package noder
 
 import (
 	"fmt"
-	"go/constant"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
@@ -53,31 +52,9 @@ func (g *irgen) expr(expr syntax.Expr) ir.Node {
 
 	base.Assert(g.exprStmtOK)
 
-	// The gc backend expects all expressions to have a concrete type, and
-	// types2 mostly satisfies this expectation already. But there are a few
-	// cases where the Go spec doesn't require converting to concrete type,
-	// and so types2 leaves them untyped. So we need to fix those up here.
-	typ := tv.Type
-	if basic, ok := typ.(*types2.Basic); ok && basic.Info()&types2.IsUntyped != 0 {
-		switch basic.Kind() {
-		case types2.UntypedNil:
-			// ok; can appear in type switch case clauses
-			// TODO(mdempsky): Handle as part of type switches instead?
-		case types2.UntypedInt, types2.UntypedFloat, types2.UntypedComplex:
-			// Untyped rhs of non-constant shift, e.g. x << 1.0.
-			// If we have a constant value, it must be an int >= 0.
-			if tv.Value != nil {
-				s := constant.ToInt(tv.Value)
-				assert(s.Kind() == constant.Int && constant.Sign(s) >= 0)
-			}
-			typ = types2.Typ[types2.Uint]
-		case types2.UntypedBool:
-			typ = types2.Typ[types2.Bool] // expression in "if" or "for" condition
-		case types2.UntypedString:
-			typ = types2.Typ[types2.String] // argument to "append" or "copy" calls
-		default:
-			base.FatalfAt(g.pos(expr), "unexpected untyped type: %v", basic)
-		}
+	typ := idealType(tv)
+	if typ == nil {
+		base.FatalfAt(g.pos(expr), "unexpected untyped type: %v", tv.Type)
 	}
 
 	// Constant expression.
diff --git a/src/cmd/compile/internal/noder/helpers.go b/src/cmd/compile/internal/noder/helpers.go
index 8efcef26cf..40f80ab528 100644
--- a/src/cmd/compile/internal/noder/helpers.go
+++ b/src/cmd/compile/internal/noder/helpers.go
@@ -11,6 +11,7 @@ import (
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
 	"cmd/internal/src"
 )
 
@@ -220,3 +221,33 @@ func IncDec(pos src.XPos, op ir.Op, x ir.Node) *ir.AssignOpStmt {
 	}
 	return ir.NewAssignOpStmt(pos, op, x, bl)
 }
+
+func idealType(tv types2.TypeAndValue) types2.Type {
+	// The gc backend expects all expressions to have a concrete type, and
+	// types2 mostly satisfies this expectation already. But there are a few
+	// cases where the Go spec doesn't require converting to concrete type,
+	// and so types2 leaves them untyped. So we need to fix those up here.
+	typ := tv.Type
+	if basic, ok := typ.(*types2.Basic); ok && basic.Info()&types2.IsUntyped != 0 {
+		switch basic.Kind() {
+		case types2.UntypedNil:
+			// ok; can appear in type switch case clauses
+			// TODO(mdempsky): Handle as part of type switches instead?
+		case types2.UntypedInt, types2.UntypedFloat, types2.UntypedComplex:
+			// Untyped rhs of non-constant shift, e.g. x << 1.0.
+			// If we have a constant value, it must be an int >= 0.
+			if tv.Value != nil {
+				s := constant.ToInt(tv.Value)
+				assert(s.Kind() == constant.Int && constant.Sign(s) >= 0)
+			}
+			typ = types2.Typ[types2.Uint]
+		case types2.UntypedBool:
+			typ = types2.Typ[types2.Bool] // expression in "if" or "for" condition
+		case types2.UntypedString:
+			typ = types2.Typ[types2.String] // argument to "append" or "copy" calls
+		default:
+			return nil
+		}
+	}
+	return typ
+}
diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index 09afbcdffb..ac08022c34 100644
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -1436,7 +1436,9 @@ func (w *writer) expr(expr syntax.Expr) {
 		if tv.Value != nil {
 			w.Code(exprConst)
 			w.pos(expr)
-			w.typ(tv.Type)
+			typ := idealType(tv)
+			assert(typ != nil)
+			w.typ(typ)
 			w.Value(tv.Value)
 
 			// TODO(mdempsky): These details are only important for backend