--- src/blackbox.c
+++ src/blackbox.c
@@ -652,7 +652,7 @@
 
 void generate_field()
 {
-  int x,y,crystal_num;
+  int x,y,crystal_num = 0;
   
   for (x=0;x<=10;x++){
     for (y=0;y<=8;y++){