diff --git a/src/verilog.y b/src/verilog.y
index 1cbbecac4..018fa99dc 100644
--- a/src/verilog.y
+++ b/src/verilog.y
@@ -30,6 +30,7 @@
 #include "V3Global.h"
 
 #define YYERROR_VERBOSE 1
+#define YYINITDEPTH 10000	// Older bisons ignore YYMAXDEPTH
 #define YYMAXDEPTH 10000
 
 // Pick up new lexer