diff --git a/src/bin/pgbench/pgbench.h b/src/bin/pgbench/pgbench.h
index e053c9e2eb6..f8b7b497d1e 100644
--- a/src/bin/pgbench/pgbench.h
+++ b/src/bin/pgbench/pgbench.h
@@ -16,11 +16,14 @@
 /*
  * This file is included outside exprscan.l, in places where we can't see
  * flex's definition of typedef yyscan_t.  Fortunately, it's documented as
- * being "void *", so we can use a macro to keep the function declarations
+ * being "void *", so we can use typedef to keep the function declarations
  * here looking like the definitions in exprscan.l.  exprparse.y and
  * pgbench.c also use this to be able to declare things as "yyscan_t".
  */
-#define yyscan_t  void *
+#ifndef YY_TYPEDEF_YY_SCANNER_T
+#define YY_TYPEDEF_YY_SCANNER_T
+typedef void *yyscan_t;
+#endif
 
 /*
  * Likewise, we can't see exprparse.y's definition of union YYSTYPE here,