diff --git a/unix/osxlaunch.c b/unix/osxlaunch.c
index 2627c642..28516185 100644
--- a/unix/osxlaunch.c
+++ b/unix/osxlaunch.c
@@ -130,11 +130,11 @@ char *get_unused_env_prefix(void)
     char **e;
 
     qhead = (struct bucket *)malloc(sizeof(struct bucket));
-    qhead->prefixlen = 0;
     if (!qhead) {
         fprintf(stderr, "out of memory\n");
         exit(1);
     }
+    qhead->prefixlen = 0;
     for (e = environ; *e; e++)
         qhead->first_node = new_node(qhead->first_node, *e, strcspn(*e, "="));