diff --git a/mode/sh.py b/mode/sh.py
index 2ff8e3c..f7a8854 100644
--- a/mode/sh.py
+++ b/mode/sh.py
@@ -47,6 +47,7 @@ class TestGrammar(Grammar):
 
 class ShGrammar(Grammar):
     rules = [
+        RegionRule(r'heredoc', r"<<(?P<heredoc>[a-zA-Z0-9_]+)", StringGrammar, r'^%(heredoc)s$'),
         PatternRule(r'sh_function', r'[a-zA-Z_][a-zA-Z0-9_]*(?= *\(\))'),
         PatternRule(r'sh_reserved', r"(?:done|do|elif|else|esac|fi|for|function|if|in|select|then|until|while|time)(?![a-zA-Z0-9_=/])"),
         RegionRule(r'case', r'case', Grammar, 'in', CaseGrammar, r'esac'),