diff --git a/doc/specs/idl.md b/doc/specs/idl.md
index 8441f32..adcbb71 100644
--- a/doc/specs/idl.md
+++ b/doc/specs/idl.md
@@ -210,6 +210,21 @@
 
     [42] Digit           ::=  ['0'-'9']
 
+## Reserved keywords
+
+    "BEGIN", "END", "__CLASS__", "__DIR__", "__FILE__", "__FUNCTION__",
+    "__LINE__", "__METHOD__", "__NAMESPACE__", "abstract", "alias", "and", "args", "as",
+    "assert", "begin", "break", "case", "catch", "class", "clone", "continue", "declare",
+    "def", "default", "del", "delete", "do", "dynamic", "elif", "else", "elseif", "elsif",
+    "end", "enddeclare", "endfor", "endforeach", "endif", "endswitch", "endwhile", "ensure",
+    "except", "exec", "finally", "float", "for", "foreach", "from", "function", "global",
+    "goto", "if", "implements", "import", "in", "inline", "instanceof", "interface", "is",
+    "lambda", "module", "native", "new", "next", "nil", "not", "or", "package", "pass",
+    "public", "print", "private", "protected", "raise", "redo", "rescue", "retry", "register",
+    "return", "self", "sizeof", "static", "super", "switch", "synchronized", "then", "this",
+    "throw", "transient", "try", "undef", "unless", "unsigned", "until", "use", "var",
+    "virtual", "volatile", "when", "while", "with", "xor", "yield" 
+
 ## Examples
 
 Here are some examples of Thrift definitions, using the Thrift IDL: