diff --git a/mrbgems/mruby-regexp/src/re_compile.c b/mrbgems/mruby-regexp/src/re_compile.c
index 9ffcab203..6ea625913 100644
--- a/mrbgems/mruby-regexp/src/re_compile.c
+++ b/mrbgems/mruby-regexp/src/re_compile.c
@@ -214,6 +214,8 @@ parse_escape(re_compiler *c)
   case 'v': return '\v';
   case 'a': return '\a';
   case 'e': return 0x1b;
+  case 'b': return '\b';  /* backspace; only reachable inside [...] since the
+                             top-level dispatcher emits RE_WBOUND for `\b` */
   default: return ch;  /* literal: \., \\, \/, \(, etc. */
   }
 }
diff --git a/mrbgems/mruby-regexp/test/regexp.rb b/mrbgems/mruby-regexp/test/regexp.rb
index 8f1499c27..e6e0a0bb6 100644
--- a/mrbgems/mruby-regexp/test/regexp.rb
+++ b/mrbgems/mruby-regexp/test/regexp.rb
@@ -47,6 +47,14 @@ assert("Regexp - character class") do
   assert_equal "abc", md[0]
 end
 
+assert("Regexp - \\b inside character class is backspace") do
+  # Outside [...], \b is the word boundary assertion; inside [...]
+  # it must mean U+0008 (backspace), matching MRI/Onigmo.
+  assert_equal "Ruby", "Ruby".gsub(/[\b]/, "X")
+  assert_equal "aXc", "a\bc".gsub(/[\b]/, "X")
+  assert_equal ["\b", "\t", "\n"], "ABC\b\t\n".scan(/[\b-\n]/)
+end
+
 assert("Regexp - dot") do
   re = Regexp.new("a.c")
   assert_true re.match?("abc")