diff --git a/mfapi/mfconn.c b/mfapi/mfconn.c
index 0322604..37270b4 100644
--- a/mfapi/mfconn.c
+++ b/mfapi/mfconn.c
@@ -94,8 +94,13 @@ const char     *mfconn_create_user_signature(mfconn * conn,
     if (conn == NULL)
         return NULL;
 
-    signature_raw = strdup_printf("%s%s%d%s",
-                                  username, password, app_id, app_key);
+    if (app_key == NULL) {
+        signature_raw = strdup_printf("%s%s%d",
+                                      username, password, app_id);
+    } else {
+        signature_raw = strdup_printf("%s%s%d%s",
+                                      username, password, app_id, app_key);
+    }
 
     SHA1((const unsigned char *)signature_raw,
          strlen(signature_raw), signature_enc);
diff --git a/mfshell/main.c b/mfshell/main.c
index 8c1abbb..1ec113f 100644
--- a/mfshell/main.c
+++ b/mfshell/main.c
@@ -21,6 +21,7 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdio.h>
 
 #include "../utils/strings.h"
 #include "mfshell.h"
@@ -51,8 +52,12 @@ int main(int argc, char *const argv[])
         opts.server = strdup("www.mediafire.com");
     }
 
-    shell = mfshell_create(35860, "2c6dq0gb2sr8rgsue5a347lzpjnaay46yjazjcjg",
+    shell = mfshell_create(35860, NULL,
                            opts.server);
+    if (shell == NULL) {
+        fprintf(stderr, "cannot create shell\n");
+        exit(1);
+    }
 
     // if at least username was set, authenticate automatically
     if (opts.username != NULL) {
diff --git a/mfshell/mfshell.c b/mfshell/mfshell.c
index b6d4205..a02ddb6 100644
--- a/mfshell/mfshell.c
+++ b/mfshell/mfshell.c
@@ -56,8 +56,6 @@ mfshell        *mfshell_create(int app_id, char *app_key, char *server)
 
     if (app_id <= 0)
         return NULL;
-    if (app_key == NULL)
-        return NULL;
     if (server == NULL)
         return NULL;
 
@@ -72,7 +70,11 @@ mfshell        *mfshell_create(int app_id, char *app_key, char *server)
     shell = (mfshell *) calloc(1, sizeof(mfshell));
 
     shell->app_id = app_id;
-    shell->app_key = strdup(app_key);
+    if (app_key == NULL) {
+        shell->app_key = NULL;
+    } else {
+        shell->app_key = strdup(app_key);
+    }
     shell->server = strdup(server);
 
     // object to track folder location
@@ -89,6 +91,9 @@ int mfshell_exec(mfshell * shell, int argc, char *const argv[])
 {
     mfcmd          *curr_cmd;
 
+    if (shell == NULL)
+        return -1;
+
     for (curr_cmd = shell->commands; curr_cmd->name != NULL; curr_cmd++) {
         if (strcmp(argv[0], curr_cmd->name) == 0) {
             return curr_cmd->handler(shell, argc, argv);
@@ -222,7 +227,8 @@ void mfshell_run(mfshell * shell)
 
 void mfshell_destroy(mfshell * shell)
 {
-    free(shell->app_key);
+    if (shell->app_key != NULL)
+        free(shell->app_key);
     free(shell->server);
     free(shell->local_working_dir);
     folder_free(shell->folder_curr);