diff --git a/src/cmd/compile/internal/typecheck/expr.go b/src/cmd/compile/internal/typecheck/expr.go
index 53d0cbf96d..83d1355fe5 100644
--- a/src/cmd/compile/internal/typecheck/expr.go
+++ b/src/cmd/compile/internal/typecheck/expr.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"go/constant"
 	"go/token"
+	"internal/types/errors"
 	"strings"
 
 	"cmd/compile/internal/base"
@@ -353,7 +354,10 @@ func tcConv(n *ir.ConvExpr) ir.Node {
 	}
 	op, why := Convertop(n.X.Op() == ir.OLITERAL, t, n.Type())
 	if op == ir.OXXX {
-		base.Fatalf("cannot convert %L to type %v%s", n.X, n.Type(), why)
+		// Due to //go:nointerface, we may be stricter than types2 here (#63333).
+		base.ErrorfAt(n.Pos(), errors.InvalidConversion, "cannot convert %L to type %v%s", n.X, n.Type(), why)
+		n.SetType(nil)
+		return n
 	}
 
 	n.SetOp(op)
diff --git a/test/fixedbugs/issue63333.go b/test/fixedbugs/issue63333.go
new file mode 100644
index 0000000000..e14b367430
--- /dev/null
+++ b/test/fixedbugs/issue63333.go
@@ -0,0 +1,15 @@
+// errorcheck -goexperiment fieldtrack
+
+// Copyright 2023 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
+
+func f(interface{ m() }) {}
+func g()                 { f(new(T)) } // ERROR "m method is marked 'nointerface'"
+
+type T struct{}
+
+//go:nointerface
+func (*T) m() {}