diff --git a/doc/specs/idl.md b/doc/specs/idl.md
index 524f4e7..ac35368 100644
--- a/doc/specs/idl.md
+++ b/doc/specs/idl.md
@@ -96,7 +96,7 @@
 
 ## Field
 
-    [16] Field           ::=  FieldID? FieldReq? FieldType Identifier ('= ConstValue)? XsdFieldOptions ListSeparator?
+    [16] Field           ::=  FieldID? FieldReq? FieldType Identifier ('=' ConstValue)? XsdFieldOptions ListSeparator?
 
 ### Field ID