diff --git a/layout/base/AccessibleCaretManager.cpp b/layout/base/AccessibleCaretManager.cpp
index f7d8eff25140..729076db1c8e 100644
--- a/layout/base/AccessibleCaretManager.cpp
+++ b/layout/base/AccessibleCaretManager.cpp
@@ -953,9 +953,14 @@ AccessibleCaretManager::ExtendPhoneNumberSelection(const nsAString& aDirection)
     // be changed after calling Selection::Modify().
     RefPtr<nsRange> oldAnchorFocusRange = anchorFocusRange->CloneRange();
 
-    // Save current Focus position, and extend the selection one char.
-    nsINode* focusNode = selection->GetFocusNode();
-    uint32_t focusOffset = selection->FocusOffset();
+    // Save current focus node, focus offset and the selected text so that
+    // we can compare them with the modified ones later.
+    nsINode* oldFocusNode = selection->GetFocusNode();
+    uint32_t oldFocusOffset = selection->FocusOffset();
+    nsAutoString oldSelectedText;
+    selection->Stringify(oldSelectedText);
+
+    // Extend the selection by one char.
     selection->Modify(NS_LITERAL_STRING("extend"),
                       aDirection,
                       NS_LITERAL_STRING("character"));
@@ -964,17 +969,22 @@ AccessibleCaretManager::ExtendPhoneNumberSelection(const nsAString& aDirection)
     }
 
     // If the selection didn't change, (can't extend further), we're done.
-    if (selection->GetFocusNode() == focusNode &&
-        selection->FocusOffset() == focusOffset) {
+    if (selection->GetFocusNode() == oldFocusNode &&
+        selection->FocusOffset() == oldFocusOffset) {
       return;
     }
 
     // If the changed selection isn't a valid phone number, we're done.
+    // Also, if the selection was extended to a new block node, the string
+    // returned by stringify() won't have a new line at the beginning or the
+    // end of the string. Therefore, if either focus node or offset is
+    // changed, but selected text is not changed, we're done, too.
     nsAutoString selectedText;
     selection->Stringify(selectedText);
-    nsAutoString phoneRegex(NS_LITERAL_STRING("(^\\+)?[0-9\\s,\\-.()*#pw]{1,30}$"));
+    nsAutoString phoneRegex(NS_LITERAL_STRING("(^\\+)?[0-9 ,\\-.()*#pw]{1,30}$"));
 
-    if (!nsContentUtils::IsPatternMatching(selectedText, phoneRegex, doc)) {
+    if (!nsContentUtils::IsPatternMatching(selectedText, phoneRegex, doc) ||
+        oldSelectedText == selectedText) {
       // Backout the undesired selection extend, restore the old anchor focus
       // range before exit.
       selection->SetAnchorFocusToRange(oldAnchorFocusRange);
diff --git a/mobile/android/tests/browser/robocop/testAccessibleCarets.html b/mobile/android/tests/browser/robocop/testAccessibleCarets.html
index df378ed46a5a..b1ab210257d5 100644
--- a/mobile/android/tests/browser/robocop/testAccessibleCarets.html
+++ b/mobile/android/tests/browser/robocop/testAccessibleCarets.html
@@ -41,5 +41,10 @@
     <br><br><br>
     <div>x<input value="DDs12">3 45<em id="bug1265750"> 678</em> 90</div>
 
+    <br><br><br>
+    <tr><td>cell</td><td><p id="bug1338445-1">012345p</p></td><td>cell</td></tr>
+    <br><br><br>
+    <div><p>p12</p><p id="bug1338445-2">p34</p><p>p56</p></div>
+    </tr>
   </body>
 </html>
diff --git a/mobile/android/tests/browser/robocop/testAccessibleCarets.js b/mobile/android/tests/browser/robocop/testAccessibleCarets.js
index 9b0b0596d7b4..b8841d04c5e9 100644
--- a/mobile/android/tests/browser/robocop/testAccessibleCarets.js
+++ b/mobile/android/tests/browser/robocop/testAccessibleCarets.js
@@ -182,6 +182,8 @@ add_task(function* testAccessibleCarets() {
   let ip_LTR_elem = doc.getElementById("LTRphone");
   let ip_RTL_elem = doc.getElementById("RTLphone");
   let bug1265750_elem = doc.getElementById("bug1265750");
+  let bug1338445_elem1 = doc.getElementById("bug1338445-1");
+  let bug1338445_elem2 = doc.getElementById("bug1338445-2");
 
   // Locate longpress midpoints for test elements, ensure expactations.
   let ce_LTR_midPoint = getCharPressPoint(doc, ce_LTR_elem, 0, "F");
@@ -197,6 +199,8 @@ add_task(function* testAccessibleCarets() {
   let ip_LTR_midPoint = getCharPressPoint(doc, ip_LTR_elem, 8, "2");
   let ip_RTL_midPoint = getCharPressPoint(doc, ip_RTL_elem, 9, "2");
   let bug1265750_midPoint = getCharPressPoint(doc, bug1265750_elem, 2, "7");
+  let bug1338445_midPoint1 = getCharPressPoint(doc, bug1338445_elem1, 3, "3");
+  let bug1338445_midPoint2 = getCharPressPoint(doc, bug1338445_elem2, 1, "3");
 
   // Longpress various LTR content elements. Test focused element against
   // expected, and selected text against expected.
@@ -228,6 +232,16 @@ add_task(function* testAccessibleCarets() {
   is(result.text, "3 45 678 90",
     "Selected phone number should match expected text.");
 
+  result = getLongPressResult(browser, bug1338445_midPoint1);
+  is(result.focusedElement, null, "Focused element should match expected.");
+  is(result.text, "012345p",
+    "Selected phone number should match expected text.");
+
+  result = getLongPressResult(browser, bug1338445_midPoint2);
+  is(result.focusedElement, null, "Focused element should match expected.");
+  is(result.text, "p34",
+    "Selected phone number should match expected text.");
+
   // Longpress various RTL content elements. Test focused element against
   // expected, and selected text against expected.
   result = getLongPressResult(browser, ce_RTL_midPoint);