diff --git a/gaboshlib/g_calc.sh b/gaboshlib/g_calc.sh
index 763547e..b9c9d62 100644
--- a/gaboshlib/g_calc.sh
+++ b/gaboshlib/g_calc.sh
@@ -27,7 +27,7 @@ function g_calc {
   read -u ${g_fd_bc_out} g_calc_result
 
   # check if there is a output
-  if [ -z $g_calc_result ]
+  if [ -z "$g_calc_result" ]
   then
     echo "${FUNCNAME} $@" 1>&2
     unset g_calc_result
@@ -48,7 +48,7 @@ function g_calc {
   [[ $g_calc_result  == *"." ]] && g_calc_result=${g_calc_result%?}
 
   # check output
-  if ! g_num_valid_number $g_calc_result
+  if ! g_num_valid_number "$g_calc_result"
   then
     echo "${FUNCNAME} $@" 1>&2
     unset g_calc_result