diff --git a/src/main.c b/src/main.c
index 72f28e3c9..391288708 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1273,12 +1273,16 @@ static void cleanarg(char *str)
  * non-zero on failure, zero on success.
  *
  * The string must start with a digit to be valid.
+ *
+ * Since this function gets called with the 'nextarg' pointer from within the
+ * getparameter a lot, we must check it for NULL before accessing the str
+ * data.
  */
 
 static int str2num(long *val, char *str)
 {
   int retcode = 0;
-  if(ISDIGIT(*str))
+  if(str && ISDIGIT(*str))
     *val = atoi(str);
   else
     retcode = 1; /* badness */