diff --git a/cjs/index.js b/cjs/index.js
index 9db2caa..b3e525f 100644
--- a/cjs/index.js
+++ b/cjs/index.js
@@ -17,6 +17,13 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
+const moveBefore = (parentNode, isConnected, node, before) => {
+  if (isConnected === node.isConnected)
+    parentNode.moveBefore(node, before);
+  else
+    parentNode.insertBefore(node, before);
+};
+
 /**
  * @param {Node} parentNode The container where children live
  * @param {Node[]} a The list of current/live children
@@ -27,6 +34,7 @@
  * @returns {Node[]} The same list of future children.
  */
 module.exports = (parentNode, a, b, get, before) => {
+  const { isConnected } = parentNode;
   const bLength = b.length;
   let aEnd = a.length;
   let bEnd = bLength;
@@ -46,7 +54,7 @@ module.exports = (parentNode, a, b, get, before) => {
           get(b[bEnd], 0)) :
         before;
       while (bStart < bEnd)
-        parentNode.insertBefore(get(b[bStart++], 1), node);
+        moveBefore(parentNode, isConnected, get(b[bStart++], 1), node);
     }
     // remove head or tail: fast path
     else if (bEnd === bStart) {
@@ -81,11 +89,9 @@ module.exports = (parentNode, a, b, get, before) => {
       // [1, 2, 3, 4, 5]
       // [1, 2, 3, 5, 6, 4]
       const node = get(a[--aEnd], -1).nextSibling;
-      parentNode.insertBefore(
-        get(b[bStart++], 1),
-        get(a[aStart++], -1).nextSibling
-      );
-      parentNode.insertBefore(get(b[--bEnd], 1), node);
+      moveBefore(parentNode, isConnected, get(b[bStart++], 1), get(a[aStart++], -1).nextSibling);
+      moveBefore(parentNode, isConnected, get(b[--bEnd], 1), node);
+
       // mark the future index as identical (yeah, it's dirty, but cheap 👍)
       // The main reason to do this, is that when a[aEnd] will be reached,
       // the loop will likely be on the fast path, as identical to b[bEnd].
@@ -131,15 +137,19 @@ module.exports = (parentNode, a, b, get, before) => {
           if (sequence > (index - bStart)) {
             const node = get(a[aStart], 0);
             while (bStart < index)
-              parentNode.insertBefore(get(b[bStart++], 1), node);
+              moveBefore(parentNode, isConnected, get(b[bStart++], 1), node);
           }
           // if the effort wasn't good enough, fallback to a replace,
           // moving both source and target indexes forward, hoping that some
           // similar node will be found later on, to go back to the fast path
           else {
-            parentNode.replaceChild(
+            // TODO: this was a replaceChild but it's not clear if fragments
+            // work this way ... -1 seems also not appropriate
+            moveBefore(
+              parentNode,
+              isConnected,
               get(b[bStart++], 1),
-              get(a[aStart++], -1)
+              get(a[aStart++], 0)
             );
           }
         }
diff --git a/esm/index.js b/esm/index.js
index a9cf2ff..ab71e47 100644
--- a/esm/index.js
+++ b/esm/index.js
@@ -16,6 +16,13 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
+const moveBefore = (parentNode, isConnected, node, before) => {
+  if (isConnected === node.isConnected)
+    parentNode.moveBefore(node, before);
+  else
+    parentNode.insertBefore(node, before);
+};
+
 /**
  * @param {Node} parentNode The container where children live
  * @param {Node[]} a The list of current/live children
@@ -26,6 +33,7 @@
  * @returns {Node[]} The same list of future children.
  */
 export default (parentNode, a, b, get, before) => {
+  const { isConnected } = parentNode;
   const bLength = b.length;
   let aEnd = a.length;
   let bEnd = bLength;
@@ -45,7 +53,7 @@ export default (parentNode, a, b, get, before) => {
           get(b[bEnd], 0)) :
         before;
       while (bStart < bEnd)
-        parentNode.insertBefore(get(b[bStart++], 1), node);
+        moveBefore(parentNode, isConnected, get(b[bStart++], 1), node);
     }
     // remove head or tail: fast path
     else if (bEnd === bStart) {
@@ -79,12 +87,10 @@ export default (parentNode, a, b, get, before) => {
       // or asymmetric too
       // [1, 2, 3, 4, 5]
       // [1, 2, 3, 5, 6, 4]
-      const node = get(a[--aEnd], -1).nextSibling;
-      parentNode.insertBefore(
-        get(b[bStart++], 1),
-        get(a[aStart++], -1).nextSibling
-      );
-      parentNode.insertBefore(get(b[--bEnd], 1), node);
+      const node = get(a[--aEnd], -0).nextSibling;
+      moveBefore(parentNode, isConnected, get(b[bStart++], 1), get(a[aStart++], -0).nextSibling);
+      moveBefore(parentNode, isConnected, get(b[--bEnd], 1), node);
+
       // mark the future index as identical (yeah, it's dirty, but cheap 👍)
       // The main reason to do this, is that when a[aEnd] will be reached,
       // the loop will likely be on the fast path, as identical to b[bEnd].
@@ -130,15 +136,19 @@ export default (parentNode, a, b, get, before) => {
           if (sequence > (index - bStart)) {
             const node = get(a[aStart], 0);
             while (bStart < index)
-              parentNode.insertBefore(get(b[bStart++], 1), node);
+              moveBefore(parentNode, isConnected, get(b[bStart++], 1), node);
           }
           // if the effort wasn't good enough, fallback to a replace,
           // moving both source and target indexes forward, hoping that some
           // similar node will be found later on, to go back to the fast path
           else {
-            parentNode.replaceChild(
+            // TODO: this was a replaceChild but it's not clear if fragments
+            // work this way ... -1 seems also not appropriate
+            moveBefore(
+              parentNode,
+              isConnected,
               get(b[bStart++], 1),
-              get(a[aStart++], -1)
+              get(a[aStart++], 0)
             );
           }
         }
diff --git a/index.js b/index.js
index bbcf0b5..29e760a 100644
--- a/index.js
+++ b/index.js
@@ -19,6 +19,10 @@ var udomdiff = (function (exports) {
    * PERFORMANCE OF THIS SOFTWARE.
    */
 
+  var moveBefore = function moveBefore(parentNode, isConnected, node, before) {
+    if (isConnected === node.isConnected) parentNode.moveBefore(node, before);else parentNode.insertBefore(node, before);
+  };
+
   /**
    * @param {Node} parentNode The container where children live
    * @param {Node[]} a The list of current/live children
@@ -29,6 +33,7 @@ var udomdiff = (function (exports) {
    * @returns {Node[]} The same list of future children.
    */
   var index = (function (parentNode, a, b, get, before) {
+    var isConnected = parentNode.isConnected;
     var bLength = b.length;
     var aEnd = a.length;
     var bEnd = bLength;
@@ -43,7 +48,7 @@ var udomdiff = (function (exports) {
         // the node to `insertBefore`, if the index is more than 0
         // must be retrieved, otherwise it's gonna be the first item.
         var node = bEnd < bLength ? bStart ? get(b[bStart - 1], -0).nextSibling : get(b[bEnd], 0) : before;
-        while (bStart < bEnd) parentNode.insertBefore(get(b[bStart++], 1), node);
+        while (bStart < bEnd) moveBefore(parentNode, isConnected, get(b[bStart++], 1), node);
       }
       // remove head or tail: fast path
       else if (bEnd === bStart) {
@@ -74,8 +79,9 @@ var udomdiff = (function (exports) {
         // [1, 2, 3, 4, 5]
         // [1, 2, 3, 5, 6, 4]
         var _node = get(a[--aEnd], -1).nextSibling;
-        parentNode.insertBefore(get(b[bStart++], 1), get(a[aStart++], -1).nextSibling);
-        parentNode.insertBefore(get(b[--bEnd], 1), _node);
+        moveBefore(parentNode, isConnected, get(b[bStart++], 1), get(a[aStart++], -1).nextSibling);
+        moveBefore(parentNode, isConnected, get(b[--bEnd], 1), _node);
+
         // mark the future index as identical (yeah, it's dirty, but cheap 👍)
         // The main reason to do this, is that when a[aEnd] will be reached,
         // the loop will likely be on the fast path, as identical to b[bEnd].
@@ -118,13 +124,15 @@ var udomdiff = (function (exports) {
             // will be processed at zero cost
             if (sequence > index - bStart) {
               var _node2 = get(a[aStart], 0);
-              while (bStart < index) parentNode.insertBefore(get(b[bStart++], 1), _node2);
+              while (bStart < index) moveBefore(parentNode, isConnected, get(b[bStart++], 1), _node2);
             }
             // if the effort wasn't good enough, fallback to a replace,
             // moving both source and target indexes forward, hoping that some
             // similar node will be found later on, to go back to the fast path
             else {
-              parentNode.replaceChild(get(b[bStart++], 1), get(a[aStart++], -1));
+              // TODO: this was a replaceChild but it's not clear if fragments
+              // work this way ... -1 seems also not appropriate
+              moveBefore(parentNode, isConnected, get(b[bStart++], 1), get(a[aStart++], 0));
             }
           }
           // otherwise move the source forward, 'cause there's nothing to do
diff --git a/min.js b/min.js
index f130b86..d3cb400 100644
--- a/min.js
+++ b/min.js
@@ -1 +1 @@
-var udomdiff=(e=>(e.default=function(e,r,i,f,l){for(var n=i.length,t=r.length,o=n,s=0,a=0,v=null;s<t||a<o;)if(t===s)for(var d=o<n?a?f(i[a-1],-0).nextSibling:f(i[o],0):l;a<o;)e.insertBefore(f(i[a++],1),d);else if(o===a)for(;s<t;)v&&v.has(r[s])||e.removeChild(f(r[s],-1)),s++;else if(r[s]===i[a])s++,a++;else if(r[t-1]===i[o-1])t--,o--;else if(r[s]===i[o-1]&&i[a]===r[t-1]){var g=f(r[--t],-1).nextSibling;e.insertBefore(f(i[a++],1),f(r[s++],-1).nextSibling),e.insertBefore(f(i[--o],1),g),r[t]=i[o]}else{if(!v)for(var v=new Map,h=a;h<o;)v.set(i[h],h++);if(v.has(r[s])){var u=v.get(r[s]);if(a<u&&u<o){for(var b=s,B=1;++b<t&&b<o&&v.get(r[b])===u+B;)B++;if(u-a<B)for(var c=f(r[s],0);a<u;)e.insertBefore(f(i[a++],1),c);else e.replaceChild(f(i[a++],1),f(r[s++],-1))}else s++}else e.removeChild(f(r[s++],-1))}return i},Object.defineProperty(e,"__esModule",{value:!0}),e))({}).default;
\ No newline at end of file
+var udomdiff=(e=>{function x(e,r,i,f){r===i.isConnected?e.moveBefore(i,f):e.insertBefore(i,f)}return e.default=function(e,r,i,f,n){for(var l=e.isConnected,o=i.length,t=r.length,s=o,a=0,v=0,d=null;a<t||v<s;)if(t===a)for(var u=s<o?v?f(i[v-1],-0).nextSibling:f(i[s],0):n;v<s;)x(e,l,f(i[v++],1),u);else if(s===v)for(;a<t;)d&&d.has(r[a])||e.removeChild(f(r[a],-1)),a++;else if(r[a]===i[v])a++,v++;else if(r[t-1]===i[s-1])t--,s--;else if(r[a]===i[s-1]&&i[v]===r[t-1]){var g=f(r[--t],-1).nextSibling;x(e,l,f(i[v++],1),f(r[a++],-1).nextSibling),x(e,l,f(i[--s],1),g),r[t]=i[s]}else{if(!d)for(var d=new Map,h=v;h<s;)d.set(i[h],h++);if(d.has(r[a])){var c=d.get(r[a]);if(v<c&&c<s){for(var b=a,m=1;++b<t&&b<s&&d.get(r[b])===c+m;)m++;if(c-v<m)for(var C=f(r[a],0);v<c;)x(e,l,f(i[v++],1),C);else x(e,l,f(i[v++],1),f(r[a++],0))}else a++}else e.removeChild(f(r[a++],-1))}return i},Object.defineProperty(e,"__esModule",{value:!0}),e})({}).default;
\ No newline at end of file
diff --git a/new.js b/new.js
index 5ede361..dc5f790 100644
--- a/new.js
+++ b/new.js
@@ -1 +1 @@
-var udomdiff=function(e){"use strict";return e.default=(e,t,i,l,r)=>{const f=i.length;let n=t.length,s=f,o=0,c=0,u=null;for(;o<n||c<s;)if(n===o){const t=s<f?c?l(i[c-1],-0).nextSibling:l(i[s],0):r;for(;c<s;)e.insertBefore(l(i[c++],1),t)}else if(s===c)for(;o<n;)u&&u.has(t[o])||e.removeChild(l(t[o],-1)),o++;else if(t[o]===i[c])o++,c++;else if(t[n-1]===i[s-1])n--,s--;else if(t[o]===i[s-1]&&i[c]===t[n-1]){const r=l(t[--n],-1).nextSibling;e.insertBefore(l(i[c++],1),l(t[o++],-1).nextSibling),e.insertBefore(l(i[--s],1),r),t[n]=i[s]}else{if(!u){u=new Map;let e=c;for(;e<s;)u.set(i[e],e++)}if(u.has(t[o])){const r=u.get(t[o]);if(c<r&&r<s){let f=o,d=1;for(;++f<n&&f<s&&u.get(t[f])===r+d;)d++;if(d>r-c){const f=l(t[o],0);for(;c<r;)e.insertBefore(l(i[c++],1),f)}else e.replaceChild(l(i[c++],1),l(t[o++],-1))}else o++}else e.removeChild(l(t[o++],-1))}return i},Object.defineProperty(e,"__esModule",{value:!0}),e}({}).default;
+var udomdiff=function(e){"use strict";const t=(e,t,n,i)=>{t===n.isConnected?e.moveBefore(n,i):e.insertBefore(n,i)};return e.default=(e,n,i,l,o)=>{const{isConnected:s}=e,f=i.length;let r=n.length,c=f,d=0,u=0,g=null;for(;d<r||u<c;)if(r===d){const n=c<f?u?l(i[u-1],-0).nextSibling:l(i[c],0):o;for(;u<c;)t(e,s,l(i[u++],1),n)}else if(c===u)for(;d<r;)g&&g.has(n[d])||e.removeChild(l(n[d],-1)),d++;else if(n[d]===i[u])d++,u++;else if(n[r-1]===i[c-1])r--,c--;else if(n[d]===i[c-1]&&i[u]===n[r-1]){const o=l(n[--r],-1).nextSibling;t(e,s,l(i[u++],1),l(n[d++],-1).nextSibling),t(e,s,l(i[--c],1),o),n[r]=i[c]}else{if(!g){g=new Map;let e=u;for(;e<c;)g.set(i[e],e++)}if(g.has(n[d])){const o=g.get(n[d]);if(u<o&&o<c){let f=d,a=1;for(;++f<r&&f<c&&g.get(n[f])===o+a;)a++;if(a>o-u){const f=l(n[d],0);for(;u<o;)t(e,s,l(i[u++],1),f)}else t(e,s,l(i[u++],1),l(n[d++],0))}else d++}else e.removeChild(l(n[d++],-1))}return i},Object.defineProperty(e,"__esModule",{value:!0}),e}({}).default;
diff --git a/test/dommy.js b/test/dommy.js
index 112520a..c733ed3 100644
--- a/test/dommy.js
+++ b/test/dommy.js
@@ -28,6 +28,7 @@ const remove = node => {
 };
 
 class Siblings {
+  get isConnected() { return true }
   get nextSibling() {
     const {parentNode} = this;
     if (parentNode) {
@@ -87,6 +88,9 @@ class Dommy extends Siblings {
     newNode.parentNode = this;
     return newNode;
   }
+  moveBefore(newNode, oldNode) {
+    this.insertBefore(newNode, oldNode);
+  }
   insertBefore(newNode, oldNode) {
     if (newNode !== oldNode) {
       remove(newNode);
diff --git a/test/index.html b/test/index.html
index 4e4376d..b44cd38 100644
--- a/test/index.html
+++ b/test/index.html
@@ -6,6 +6,7 @@
   <script src="../index.js"></script>
   <script src="test.js"></script>
   <script>
+  Node.prototype.moveBefore = Node.prototype.insertBefore;
   window.onload = test;
   </script>
 </head>
diff --git a/test/index.js b/test/index.js
index 86f298a..772e776 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,6 +1,6 @@
 global.document = {
   createElement: function (tagName) {
-    return {tagName: tagName, value: '\n'};
+    return {tagName: tagName, value: '\n', isConnected: true};
   },
   createTextNode: function (value) {
     return Object.defineProperty(
@@ -14,6 +14,7 @@ global.document = {
   },
   importNode: function () {},
   body: {
+    isConnected: true,
     get lastElementChild() {
       return this.childNodes[this.childNodes.length - 1];
     },
@@ -26,6 +27,9 @@ global.document = {
       node.parentNode = this;
     },
     childNodes: [],
+    moveBefore: function (before, after) {
+      this.insertBefore(before, after);
+    },
     insertBefore: function (before, after) {
       if (before !== after) {
         this.removeChild(before);