diff --git a/accessible/generic/HyperTextAccessible.cpp b/accessible/generic/HyperTextAccessible.cpp
index d95844bdb65e..1a8cabf9bddf 100644
--- a/accessible/generic/HyperTextAccessible.cpp
+++ b/accessible/generic/HyperTextAccessible.cpp
@@ -2206,7 +2206,10 @@ HyperTextAccessible::GetSpellTextAttr(nsINode* aNode,
                                      prevRange->EndOffset());
     }
 
-    if (startOffset > *aStartOffset)
+    // The previous range might not be within this accessible. In that case,
+    // DOMPointToOffset returns length as a fallback. We don't want to use
+    // that offset if so, hence the startOffset < *aEndOffset check.
+    if (startOffset > *aStartOffset && startOffset < *aEndOffset)
       *aStartOffset = startOffset;
 
     if (endOffset < *aEndOffset)
@@ -2223,7 +2226,10 @@ HyperTextAccessible::GetSpellTextAttr(nsINode* aNode,
   startOffset = DOMPointToOffset(prevRange->GetEndContainer(),
                                  prevRange->EndOffset());
 
-  if (startOffset > *aStartOffset)
+  // The previous range might not be within this accessible. In that case,
+  // DOMPointToOffset returns length as a fallback. We don't want to use
+  // that offset if so, hence the startOffset < *aEndOffset check.
+  if (startOffset > *aStartOffset && startOffset < *aEndOffset)
     *aStartOffset = startOffset;
 }
 
diff --git a/accessible/tests/mochitest/textattrs/a11y.ini b/accessible/tests/mochitest/textattrs/a11y.ini
index 046bd57e815b..98855d84b5b1 100644
--- a/accessible/tests/mochitest/textattrs/a11y.ini
+++ b/accessible/tests/mochitest/textattrs/a11y.ini
@@ -5,3 +5,4 @@ support-files =
 
 [test_general.html]
 [test_invalid.html]
+[test_spelling.html]
diff --git a/accessible/tests/mochitest/textattrs/test_spelling.html b/accessible/tests/mochitest/textattrs/test_spelling.html
new file mode 100644
index 000000000000..030b20c3be2c
--- /dev/null
+++ b/accessible/tests/mochitest/textattrs/test_spelling.html
@@ -0,0 +1,53 @@
+<html>
+
+<head>
+  <title>Spell check text attribute tests</title>
+  <meta charset="utf-8" />
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css" />
+
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+
+  <script type="application/javascript"
+          src="../common.js"></script>
+  <script type="application/javascript"
+          src="../attributes.js"></script>
+  <script type="application/javascript"
+          src="../events.js"></script>
+
+  <script type="application/javascript">
+    async function doTest() {
+      const misspelledAttrs = {"invalid": "spelling"};
+
+      let editable = document.getElementById("div_after_misspelling");
+      // The attr change event gets fired on the last accessible containing a
+      // spelling error.
+      let spellDone = waitForEventPromise(EVENT_TEXT_ATTRIBUTE_CHANGED, "div_after_misspelling_div2");
+      editable.focus();
+      await spellDone;
+      testTextAttrs("div_after_misspelling_div1", 0, {}, {}, 0, 5, true);
+      testTextAttrs("div_after_misspelling_div1", 5, misspelledAttrs, {}, 5, 9, true);
+      testTextAttrs("div_after_misspelling_div2", 0, {}, {}, 0, 5, true);
+      testTextAttrs("div_after_misspelling_div2", 5, misspelledAttrs, {}, 5, 9, true);
+
+      SimpleTest.finish();
+    }
+
+    SimpleTest.waitForExplicitFinish();
+    addA11yLoadEvent(doTest);
+  </script>
+</head>
+<body>
+  <p id="display"></p>
+  <div id="content" style="display: none"></div>
+  <pre id="test">
+  </pre>
+
+  <!-- Text attribute offsets for accessibles after first spelling error (bug 1479678) -->
+  <div id="div_after_misspelling" contenteditable="true" spellcheck="true" lang="en-US">
+    <div id="div_after_misspelling_div1">Test tset</div>
+    <div id="div_after_misspelling_div2">test tset</div>
+  </div>
+
+</body>
+</html>
