--- a/toolkit/content/tests/chrome/findbar_window.xul
+++ b/toolkit/content/tests/chrome/findbar_window.xul
@@ -147,16 +147,17 @@
       yield openFindbar();
       yield testFailedStringReset();
       gFindBar.close();
       yield testQuickFindClose();
       // TODO: This doesn't seem to work when the findbar is connected to a
       //       remote browser element.
       if (!gBrowser.hasAttribute("remote"))
         yield testFindAgainNotFound();
+      yield testToggleEntireWord();
     }
 
     function* testFindbarSelection() {
       function checkFindbarState(aTestName, aExpSelection) {
         ok(!gFindBar.hidden, "testFindbarSelection: failed to open findbar: " + aTestName);
         ok(document.commandDispatcher.focusedElement == gFindBar._findField.inputField,
            "testFindbarSelection: find field is not focused: " + aTestName);
         if (!gHasFindClipboard) {
@@ -230,19 +231,19 @@
         };
         setTimeout(_delayedCheckStatusText, 100);
       });
     }
 
     function promiseFindResult() {
       return new Promise(resolve => {
         let listener = {
-          onFindResult: function() {
+          onFindResult: function(result) {
             gFindBar.browser.finder.removeResultListener(listener);
-            resolve();
+            resolve(result);
           }
         };
         gFindBar.browser.finder.addResultListener(listener);
       });
     }
 
     function promiseMatchesCountResult() {
       return new Promise(resolve => {
@@ -645,16 +646,34 @@
       yield enterStringIntoFindField(SEARCH_TEXT);
       gFindBar.close();
       ok(gFindBar.hidden, "The findbar is closed.");
       promise = promiseFindResult();
       gFindBar.onFindAgainCommand();
       yield promise;
       ok(gFindBar.hidden, "Successful Find Again leaves the find bar closed.");
     }
+
+    function* testToggleEntireWord() {
+      yield openFindbar();
+      let promise = promiseFindResult();
+      yield enterStringIntoFindField("Tex", false);
+      let result = yield promise;
+      is(result.result, Ci.nsITypeAheadFind.FIND_FOUND, "Text should be found");
+
+      yield new Promise(resolve => setTimeout(resolve, ITERATOR_TIMEOUT));
+      promise = promiseFindResult();
+      let check = gFindBar.getElement("find-entire-word");
+      check.click();
+      result = yield promise;
+      is(result.result, Ci.nsITypeAheadFind.FIND_NOTFOUND, "Text should NOT be found");
+
+      check.click();
+      gFindBar.close(true);
+    }
   ]]></script>
 
   <commandset>
     <command id="cmd_find" oncommand="document.getElementById('FindToolbar').onFindCommand();"/>
   </commandset>
   <browser type="content-primary" flex="1" id="content" src="about:blank"/>
   <browser type="content-primary" flex="1" id="content-remote" remote="true" src="about:blank"/>
   <findbar id="FindToolbar" browserid="content"/>

--- a/toolkit/content/widgets/findbar.xml
+++ b/toolkit/content/widgets/findbar.xml
@@ -194,17 +194,17 @@
                          oncommand="_setCaseSensitivity(this.checked ? 1 : 0);"
                          type="checkbox"
                          xbl:inherits="accesskey=matchcaseaccesskey"/>
       <xul:toolbarbutton anonid="find-entire-word"
                          class="findbar-entire-word findbar-button tabbable"
                          label="&entireWord.label;"
                          accesskey="&entireWord.accesskey;"
                          tooltiptext="&entireWord.tooltiptext;"
-                         oncommand="_setEntireWord(this.checked);"
+                         oncommand="toggleEntireWord(this.checked);"
                          type="checkbox"
                          xbl:inherits="accesskey=entirewordaccesskey"/>
       <xul:label anonid="match-case-status" class="findbar-find-fast"/>
       <xul:label anonid="entire-word-status" class="findbar-find-fast"/>
       <xul:label anonid="found-matches" class="findbar-find-fast found-matches" hidden="true"/>
       <xul:image anonid="find-status-icon" class="findbar-find-fast find-status-icon"/>
       <xul:description anonid="find-status"
                        control="findbar-textbox"
@@ -338,19 +338,17 @@
             case "accessibility.typeaheadfind.linksonly":
               this._self._typeAheadLinksOnly = prefsvc.getBoolPref(aPrefName);
               break;
             case "accessibility.typeaheadfind.casesensitive":
               this._self._setCaseSensitivity(prefsvc.getIntPref(aPrefName));
               break;
             case "findbar.entireword":
               this._self._entireWord = prefsvc.getBoolPref(aPrefName);
-              this._self._updateEntireWord();
-              // Update the matches count.
-              this._updateMatchesCount(this.nsITypeAheadFind.FIND_FOUND);
+              this._self.toggleEntireWord(this._self._entireWord, true);
               break;
             case "findbar.highlightAll":
               this._self.toggleHighlight(prefsvc.getBoolPref(aPrefName), true);
               break;
             case "findbar.modalHighlight":
               this._self._useModalHighlight = prefsvc.getBoolPref(aPrefName);
               if (this._self.browser.finder)
                 this._self.browser.finder.onModalHighlightChange(this._self._useModalHighlight);
@@ -633,17 +631,17 @@
 
           this._dispatchFindEvent("casesensitivitychange");
         ]]></body>
       </method>
 
       <!--
         - Updates the entire-word mode of the findbar and its UI.
         -->
-      <method name="_updateEntireWord">
+      <method name="_setEntireWord">
         <body><![CDATA[
           let entireWord = this._entireWord;
           let checkbox = this.getElement("find-entire-word");
           let statusLabel = this.getElement("entire-word-status");
           checkbox.checked = entireWord;
 
           statusLabel.value = entireWord ? this._entireWordStr : "";
 
@@ -657,27 +655,28 @@
         ]]></body>
       </method>
 
       <!--
         - Sets the findbar entire-word mode
         - @param aEntireWord (boolean)
         - Whether or not entire-word mode should be turned on.
         -->
-      <method name="_setEntireWord">
+      <method name="toggleEntireWord">
         <parameter name="aEntireWord"/>
+        <parameter name="aFromPrefObserver"/>
         <body><![CDATA[
-          let prefsvc =
-            Components.classes["@mozilla.org/preferences-service;1"]
-                      .getService(Components.interfaces.nsIPrefBranch);
+          if (!aFromPrefObserver) {
+            // Just set the pref; our observer will change the find bar behavior.
+            this._prefsvc.setBoolPref("findbar.entireword", aEntireWord);
+            return;
+          }
 
-          // Just set the pref; our observer will change the find bar behavior.
-          prefsvc.setBoolPref("findbar.entireword", aEntireWord);
-
-          this._maybeHighlightAll();
+          this._findFailedString = null;
+          this._find();
         ]]></body>
       </method>
 
       <field name="_strBundle">null</field>
       <property name="strBundle">
         <getter><![CDATA[
           if (!this._strBundle) {
             this._strBundle =
@@ -966,17 +965,17 @@
             if (node == wrapper || node == foundMatches)
                continue;
             node.hidden = showMinimalUI;
           }
           this.getElement("find-next").hidden =
             this.getElement("find-previous").hidden = showMinimalUI;
           foundMatches.hidden = showMinimalUI || !foundMatches.value;
           this._updateCaseSensitivity();
-          this._updateEntireWord();
+          this._setEntireWord();
           this._setHighlightAll();
 
           if (showMinimalUI)
             this._findField.classList.add("minimal");
           else
             this._findField.classList.remove("minimal");
 
           if (this._findMode == this.FIND_TYPEAHEAD)
@@ -1014,17 +1013,17 @@
             // initial prefilling is ignored if it hasn't happened yet.
             if (this._startFindDeferred) {
               this._startFindDeferred.resolve();
               this._startFindDeferred = null;
             }
 
             this._enableFindButtons(val);
             this._updateCaseSensitivity(val);
-            this._updateEntireWord();
+            this._setEntireWord();
 
             this.browser.finder.fastFind(val, this._findMode == this.FIND_LINKS,
                                          this._findMode != this.FIND_NORMAL);
           }
 
           if (this._findMode != this.FIND_NORMAL)
             this._setFindCloseTimeout();