diff --git a/editor/libeditor/HTMLEditUtils.cpp b/editor/libeditor/HTMLEditUtils.cpp
index 047e0dd7e6e8..8c3d09c1e219 100644
--- a/editor/libeditor/HTMLEditUtils.cpp
+++ b/editor/libeditor/HTMLEditUtils.cpp
@@ -224,6 +224,12 @@ bool HTMLEditUtils::IsBlockElement(const nsIContent& aContent,
   if (MOZ_UNLIKELY(!aContent.IsElement())) {
     return false;
   }
+  // If it's a <br>, we should always treat it as an inline element because
+  // its preceding collapse white-spaces and another <br> works same as usual
+  // even if you set its style to `display:block`.
+  if (aContent.IsHTMLElement(nsGkAtoms::br)) {
+    return false;
+  }
   if (!StaticPrefs::editor_block_inline_check_use_computed_style() ||
       aBlockInlineCheck == BlockInlineCheck::UseHTMLDefaultStyle) {
     return IsHTMLBlockElementByDefault(aContent);
@@ -271,6 +277,12 @@ bool HTMLEditUtils::IsInlineContent(const nsIContent& aContent,
   if (!aContent.IsElement()) {
     return true;
   }
+  // If it's a <br>, we should always treat it as an inline element because
+  // its preceding collapse white-spaces and another <br> works same as usual
+  // even if you set its style to `display:block`.
+  if (aContent.IsHTMLElement(nsGkAtoms::br)) {
+    return true;
+  }
   if (!StaticPrefs::editor_block_inline_check_use_computed_style() ||
       aBlockInlineCheck == BlockInlineCheck::UseHTMLDefaultStyle) {
     return !IsHTMLBlockElementByDefault(aContent);
diff --git a/testing/web-platform/tests/editing/other/inserttext-at-end-of-block-when-br-always-block.html b/testing/web-platform/tests/editing/other/inserttext-at-end-of-block-when-br-always-block.html
new file mode 100644
index 000000000000..922b8bd1c862
--- /dev/null
+++ b/testing/web-platform/tests/editing/other/inserttext-at-end-of-block-when-br-always-block.html
@@ -0,0 +1,36 @@
+<!doctype html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>Typing white-space and another character at end of a block should preserve the white-space when br element is always block</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+br { display: block; }
+</style>
+<script>
+"use strict";
+
+addEventListener("load", () => {
+  test(
+    () => {
+      const editingHost = document.querySelector("div[contenteditable]");
+      editingHost.focus();
+      getSelection().collapse(editingHost.firstChild, "abc".length);
+      document.execCommand("insertText", false, " ");
+      document.execCommand("insertText", false, "d");
+      assert_in_array(
+        editingHost.innerHTML,
+        [
+          "abc d",
+          "abc d<br>",
+        ]
+      );
+    },
+    "Inserting white-space and a character at block end should keep the white-space even before block <br> element"
+  );
+}, {once: true});
+</script>
+</head>
+<body><div contenteditable>abc</div></body>
+</html>
