diff --git a/index.js b/index.js
index 9481391..f7d58cd 100644
--- a/index.js
+++ b/index.js
@@ -19,6 +19,8 @@ function rfdc (opts) {
     [Set, (o, fn) => new Set(cloneArray(Array.from(o), fn))]
   ].concat(opts.constructorHandlers || []))
 
+  let handler = null
+
   return opts.proto ? cloneProto : clone
 
   function cloneArray (a, fn) {
@@ -29,8 +31,8 @@ function rfdc (opts) {
       const cur = a[k]
       if (typeof cur !== 'object' || cur === null) {
         a2[k] = cur
-      } else if (cur.constructor !== Object && constructorHandlers.has(cur.constructor)) {
-        a2[k] = constructorHandlers.get(cur.constructor)(cur, fn)
+      } else if (cur.constructor !== Object && (handler = constructorHandlers.get(cur.constructor))) {
+        a2[k] = handler(cur, fn)
       } else if (ArrayBuffer.isView(cur)) {
         a2[k] = copyBuffer(cur)
       } else {
@@ -43,8 +45,8 @@ function rfdc (opts) {
   function clone (o) {
     if (typeof o !== 'object' || o === null) return o
     if (Array.isArray(o)) return cloneArray(o, clone)
-    if (o.constructor !== Object && constructorHandlers.has(o.constructor)) {
-      return constructorHandlers.get(o.constructor)(o, clone)
+    if (o.constructor !== Object && (handler = constructorHandlers.get(o.constructor))) {
+      return handler(o, clone)
     }
     const o2 = {}
     for (const k in o) {
@@ -52,8 +54,8 @@ function rfdc (opts) {
       const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
-      } else if (cur.constructor !== Object && constructorHandlers.has(cur.constructor)) {
-        o2[k] = constructorHandlers.get(cur.constructor)(cur, clone)
+      } else if (cur.constructor !== Object && (handler = constructorHandlers.get(cur.constructor))) {
+        o2[k] = handler(cur, clone)
       } else if (ArrayBuffer.isView(cur)) {
         o2[k] = copyBuffer(cur)
       } else {
@@ -66,16 +68,16 @@ function rfdc (opts) {
   function cloneProto (o) {
     if (typeof o !== 'object' || o === null) return o
     if (Array.isArray(o)) return cloneArray(o, cloneProto)
-    if (o.constructor !== Object && constructorHandlers.has(o.constructor)) {
-      return constructorHandlers.get(o.constructor)(o, cloneProto)
+    if (o.constructor !== Object && (handler = constructorHandlers.get(o.constructor))) {
+      return handler(o, cloneProto)
     }
     const o2 = {}
     for (const k in o) {
       const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
-      } else if (cur.constructor !== Object && constructorHandlers.has(cur.constructor)) {
-        o2[k] = constructorHandlers.get(cur.constructor)(cur, cloneProto)
+      } else if (cur.constructor !== Object && (handler = constructorHandlers.get(cur.constructor))) {
+        o2[k] = handler(cur, cloneProto)
       } else if (ArrayBuffer.isView(cur)) {
         o2[k] = copyBuffer(cur)
       } else {
@@ -96,6 +98,7 @@ function rfdcCircles (opts) {
     [Set, (o, fn) => new Set(cloneArray(Array.from(o), fn))]
   ].concat(opts.constructorHandlers || []))
 
+  let handler = null
   return opts.proto ? cloneProto : clone
 
   function cloneArray (a, fn) {
@@ -106,8 +109,8 @@ function rfdcCircles (opts) {
       const cur = a[k]
       if (typeof cur !== 'object' || cur === null) {
         a2[k] = cur
-      } else if (cur.constructor !== Object && constructorHandlers.has(cur.constructor)) {
-        a2[k] = constructorHandlers.get(cur.constructor)(cur, fn)
+      } else if (cur.constructor !== Object && (handler = constructorHandlers.get(cur.constructor))) {
+        a2[k] = handler(cur, fn)
       } else if (ArrayBuffer.isView(cur)) {
         a2[k] = copyBuffer(cur)
       } else {
@@ -125,8 +128,8 @@ function rfdcCircles (opts) {
   function clone (o) {
     if (typeof o !== 'object' || o === null) return o
     if (Array.isArray(o)) return cloneArray(o, clone)
-    if (o.constructor !== Object && constructorHandlers.has(o.constructor)) {
-      return constructorHandlers.get(o.constructor)(o, clone)
+    if (o.constructor !== Object && (handler = constructorHandlers.get(o.constructor))) {
+      return handler(o, clone)
     }
     const o2 = {}
     refs.push(o)
@@ -136,8 +139,8 @@ function rfdcCircles (opts) {
       const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
-      } else if (cur.constructor !== Object && constructorHandlers.has(cur.constructor)) {
-        o2[k] = constructorHandlers.get(cur.constructor)(cur, clone)
+      } else if (cur.constructor !== Object && (handler = constructorHandlers.get(cur.constructor))) {
+        o2[k] = handler(cur, clone)
       } else if (ArrayBuffer.isView(cur)) {
         o2[k] = copyBuffer(cur)
       } else {
@@ -157,8 +160,8 @@ function rfdcCircles (opts) {
   function cloneProto (o) {
     if (typeof o !== 'object' || o === null) return o
     if (Array.isArray(o)) return cloneArray(o, cloneProto)
-    if (o.constructor !== Object && constructorHandlers.has(o.constructor)) {
-      return constructorHandlers.get(o.constructor)(o, cloneProto)
+    if (o.constructor !== Object && (handler = constructorHandlers.get(o.constructor))) {
+      return handler(o, cloneProto)
     }
     const o2 = {}
     refs.push(o)
@@ -167,8 +170,8 @@ function rfdcCircles (opts) {
       const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
-      } else if (cur.constructor !== Object && constructorHandlers.has(cur.constructor)) {
-        o2[k] = constructorHandlers.get(cur.constructor)(cur, cloneProto)
+      } else if (cur.constructor !== Object && (handler = constructorHandlers.get(cur.constructor))) {
+        o2[k] = handler(cur, cloneProto)
       } else if (ArrayBuffer.isView(cur)) {
         o2[k] = copyBuffer(cur)
       } else {