diff --git a/support/xhpast/parser.y b/support/xhpast/parser.y
--- a/support/xhpast/parser.y
+++ b/support/xhpast/parser.y
@@ -69,7 +69,7 @@
 %expect 5
 // 2: PHP's if/else grammar
 // 7: expr '[' dim_offset ']' -- shift will default to first grammar
-%name-prefix = "xhpast"
+%name-prefix "xhpast"
 %pure-parser
 %parse-param { void* yyscanner }
 %parse-param { xhpast::Node** root }