diff --git a/src/cmd/compile/internal/typecheck/const.go b/src/cmd/compile/internal/typecheck/const.go
index 5a35eeade9..761b043794 100644
--- a/src/cmd/compile/internal/typecheck/const.go
+++ b/src/cmd/compile/internal/typecheck/const.go
@@ -633,6 +633,17 @@ func defaultlit2(l ir.Node, r ir.Node, force bool) (ir.Node, ir.Node) {
 	if l.Type() == nil || r.Type() == nil {
 		return l, r
 	}
+
+	if !l.Type().IsInterface() && !r.Type().IsInterface() {
+		// Can't mix bool with non-bool, string with non-string.
+		if l.Type().IsBoolean() != r.Type().IsBoolean() {
+			return l, r
+		}
+		if l.Type().IsString() != r.Type().IsString() {
+			return l, r
+		}
+	}
+
 	if !l.Type().IsUntyped() {
 		r = convlit(r, l.Type())
 		return l, r
@@ -647,17 +658,10 @@ func defaultlit2(l ir.Node, r ir.Node, force bool) (ir.Node, ir.Node) {
 		return l, r
 	}
 
-	// Can't mix bool with non-bool, string with non-string, or nil with anything (untyped).
-	if l.Type().IsBoolean() != r.Type().IsBoolean() {
-		return l, r
-	}
-	if l.Type().IsString() != r.Type().IsString() {
-		return l, r
-	}
+	// Can't mix nil with anything untyped.
 	if ir.IsNil(l) || ir.IsNil(r) {
 		return l, r
 	}
-
 	t := defaultType(mixUntyped(l.Type(), r.Type()))
 	l = convlit(l, t)
 	r = convlit(r, t)
diff --git a/test/fixedbugs/issue46749.go b/test/fixedbugs/issue46749.go
new file mode 100644
index 0000000000..63ed19795e
--- /dev/null
+++ b/test/fixedbugs/issue46749.go
@@ -0,0 +1,37 @@
+// errorcheck
+
+// Copyright 2021 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 s string
+var b bool
+var i int
+var iface interface{}
+
+var (
+	_ = "" + b   // ERROR "invalid operation.*mismatched types.*untyped string and bool"
+	_ = "" + i   // ERROR "invalid operation.*mismatched types.*untyped string and int"
+	_ = "" + nil // ERROR "invalid operation.*mismatched types.*untyped string and nil"
+)
+
+var (
+	_ = s + false // ERROR "invalid operation.*mismatched types.*string and untyped bool"
+	_ = s + 1     // ERROR "invalid operation.*mismatched types.*string and untyped int"
+	_ = s + nil   // ERROR "invalid operation.*mismatched types.*string and nil"
+)
+
+var (
+	_ = "" + false // ERROR "invalid operation.*mismatched types.*untyped string and untyped bool"
+	_ = "" + 1     // ERROR "invalid operation.*mismatched types.*untyped string and untyped int"
+)
+
+var (
+	_ = b + 1         // ERROR "invalid operation.*mismatched types.*bool and untyped int"
+	_ = i + false     // ERROR "invalid operation.*mismatched types.*int and untyped bool"
+	_ = iface + 1     // ERROR "invalid operation.*mismatched types.*interface {} and int"
+	_ = iface + 1.0   // ERROR "invalid operation.*mismatched types.*interface {} and float64"
+	_ = iface + false // ERROR "invalid operation.*mismatched types.*interface {} and bool"
+)
diff --git a/test/run.go b/test/run.go
index 5e60de7624..d7f5d02391 100644
--- a/test/run.go
+++ b/test/run.go
@@ -2002,4 +2002,5 @@ var excluded = map[string]bool{
 	"fixedbugs/issue7525c.go":  true, // types2 reports init cycle error on different line - ok otherwise
 	"fixedbugs/issue7525d.go":  true, // types2 reports init cycle error on different line - ok otherwise
 	"fixedbugs/issue7525e.go":  true, // types2 reports init cycle error on different line - ok otherwise
+	"fixedbugs/issue46749.go":  true, // types2 reports can not convert error instead of type mismatched
 }