diff --git a/info/labs/amy-specification/AmySpec.md b/info/labs/amy-specification/AmySpec.md
index 6d58db0e7da53f92876f1c6ffaeb68cabe59e9eb..4bb8bd927c78ff3089cff2c2229f7f149d30a50e 100644
--- a/info/labs/amy-specification/AmySpec.md
+++ b/info/labs/amy-specification/AmySpec.md
@@ -230,7 +230,7 @@ Figure 2: Lexical rules for Amy
 IntLiteral ::= Digit+
 
 Id ::= Alpha AlphaNum∗ (and not a reserved word)
-AlphaNum ::= Alpha | Digit |
+AlphaNum ::= Alpha | Digit | _
 Alpha ::= [a-z] | [A-Z]
 Digit ::= [0-9]