diff --git a/ssa/interp/interp.go b/ssa/interp/interp.go
index 59c81cd9..5d8cf0fd 100644
--- a/ssa/interp/interp.go
+++ b/ssa/interp/interp.go
@@ -613,6 +613,8 @@ func setGlobal(i *interpreter, pkg *ssa.Package, name string, v value) {
 	panic("no global variable: " + pkg.Object.Path() + "." + name)
 }
 
+var stdSizes = types.StdSizes{WordSize: 8, MaxAlign: 8}
+
 // Interpret interprets the Go program whose main package is mainpkg.
 // mode specifies various interpreter options.  filename and args are
 // the initial values of os.Args for the target program.
@@ -659,7 +661,7 @@ func Interpret(mainpkg *ssa.Package, mode Mode, filename string, args []string)
 
 		case "runtime":
 			// (Assumes no custom Sizeof used during SSA construction.)
-			sz := types.DefaultSizeof(pkg.Object.Scope().Lookup("MemStats").Type())
+			sz := stdSizes.Sizeof(pkg.Object.Scope().Lookup("MemStats").Type())
 			setGlobal(i, pkg, "sizeof_C_MStats", uintptr(sz))
 
 		case "os":
diff --git a/ssa/interp/reflect.go b/ssa/interp/reflect.go
index ef74a2da..f2048f2d 100644
--- a/ssa/interp/reflect.go
+++ b/ssa/interp/reflect.go
@@ -162,7 +162,7 @@ func ext۰reflect۰rtype۰Out(fn *ssa.Function, args []value) value {
 func ext۰reflect۰rtype۰Size(fn *ssa.Function, args []value) value {
 	// Signature: func (t reflect.rtype) uintptr
 	// (Assumes no custom Sizeof used during SSA construction.)
-	return uintptr(types.DefaultSizeof(args[0].(rtype).t))
+	return uintptr(stdSizes.Sizeof(args[0].(rtype).t))
 }
 
 func ext۰reflect۰rtype۰String(fn *ssa.Function, args []value) value {