--- a/common/fractals.c	2020-07-05 13:36:44.378426423 -0000
+++ a/common/fractals.c	2020-07-05 13:36:57.308426334 -0000
@@ -3437,7 +3437,7 @@
 #undef K
 #undef L
 
-double b_const;
+extern double b_const;
 
 int DivideBrot5Setup(void)
 {