diff --git a/gaboshlib/g_calc.sh b/gaboshlib/g_calc.sh
index 302fcaf..15dbd20 100644
--- a/gaboshlib/g_calc.sh
+++ b/gaboshlib/g_calc.sh
@@ -3,7 +3,7 @@ function g_calc {
   # Use bc in backround for multiple bc's running much faster
   if [ -z "${g_bc_running}" ]
   then
-    g_rnd=$RANDOM
+    g_rnd=$$
     mkdir -p ${g_tmp}/${g_rnd}
     [ -p ${g_tmp}/${g_rnd}/bc-in ] || mkfifo ${g_tmp}/${g_rnd}/bc-in
     [ -p ${g_tmp}/${g_rnd}/bc-out ] || mkfifo ${g_tmp}/${g_rnd}/bc-out