diff --git a/mfshell/commands/changes.c b/mfshell/commands/changes.c
index 97101a1..ce93159 100644
--- a/mfshell/commands/changes.c
+++ b/mfshell/commands/changes.c
@@ -38,6 +38,11 @@ int mfshell_cmd_changes(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     switch (argc) {
         case 1:
             revision = 0;
@@ -54,6 +59,11 @@ int mfshell_cmd_changes(mfshell * mfshell, int argc, char *const argv[])
     retval = mfconn_api_device_get_changes(mfshell->conn, revision, &changes);
     mfconn_update_secret_key(mfshell->conn);
 
+    if (retval != 0) {
+        fprintf(stderr, "mfconn_api_device_get_changes failed\n");
+        return -1;
+    }
+
     for (i = 0; changes[i].change != MFCONN_DEVICE_CHANGE_END; i++) {
         switch (changes[i].change) {
             case MFCONN_DEVICE_CHANGE_DELETED_FOLDER:
diff --git a/mfshell/commands/chdir.c b/mfshell/commands/chdir.c
index 10fc157..34dbbd1 100644
--- a/mfshell/commands/chdir.c
+++ b/mfshell/commands/chdir.c
@@ -77,9 +77,18 @@ int mfshell_cmd_chdir(mfshell * mfshell, int argc, char *const argv[])
         folder_set_key(folder_new, NULL);
         retval = 0;
     } else {
+        if (mfshell->conn == NULL) {
+            fprintf(stderr, "conn is NULL\n");
+            return -1;
+        }
         retval = mfconn_api_folder_get_info(mfshell->conn,
                                             folder_new, (char *)folderkey);
         mfconn_update_secret_key(mfshell->conn);
+
+        if (retval != 0) {
+            fprintf(stderr, "mfconn_api_folder_get_info failed\n");
+            return -1;
+        }
     }
 
     if (retval == 0) {
diff --git a/mfshell/commands/file.c b/mfshell/commands/file.c
index d57318e..989279b 100644
--- a/mfshell/commands/file.c
+++ b/mfshell/commands/file.c
@@ -38,6 +38,11 @@ int mfshell_cmd_file(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 2) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
@@ -55,11 +60,13 @@ int mfshell_cmd_file(mfshell * mfshell, int argc, char *const argv[])
     file = file_alloc();
 
     retval = mfconn_api_file_get_info(mfshell->conn, file, (char *)quickkey);
-    if (retval != 0) {
-        fprintf(stderr, "api call unsuccessful\n");
-    }
     mfconn_update_secret_key(mfshell->conn);
 
+    if (retval != 0) {
+        fprintf(stderr, "mfconn_api_file_get_info failed\n");
+        return -1;
+    }
+
     quickkey = file_get_key(file);
     name = file_get_name(file);
     hash = file_get_hash(file);
diff --git a/mfshell/commands/folder.c b/mfshell/commands/folder.c
index 17aced2..764d716 100644
--- a/mfshell/commands/folder.c
+++ b/mfshell/commands/folder.c
@@ -52,6 +52,11 @@ int mfshell_cmd_folder(mfshell * mfshell, int argc, char *const argv[])
         return -1;
     }
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     switch (argc) {
         case 1:
             folderkey = NULL;
diff --git a/mfshell/commands/get.c b/mfshell/commands/get.c
index 408c388..119a1ec 100644
--- a/mfshell/commands/get.c
+++ b/mfshell/commands/get.c
@@ -42,6 +42,11 @@ int mfshell_cmd_get(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 2) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
diff --git a/mfshell/commands/links.c b/mfshell/commands/links.c
index a32ec17..1bb571c 100644
--- a/mfshell/commands/links.c
+++ b/mfshell/commands/links.c
@@ -39,6 +39,11 @@ int mfshell_cmd_links(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 2) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
diff --git a/mfshell/commands/list.c b/mfshell/commands/list.c
index b9c75fa..c917df2 100644
--- a/mfshell/commands/list.c
+++ b/mfshell/commands/list.c
@@ -38,6 +38,11 @@ int mfshell_cmd_list(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 1) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
@@ -50,6 +55,10 @@ int mfshell_cmd_list(mfshell * mfshell, int argc, char *const argv[])
                                       &folder_result, NULL);
     mfconn_update_secret_key(mfshell->conn);
 
+    if (folder_result == NULL) {
+        return -1;
+    }
+
     for (i = 0; folder_result[i] != NULL; i++) {
         printf("%s %s\n", folder_get_name(folder_result[i]),
                folder_get_key(folder_result[i]));
diff --git a/mfshell/commands/mkdir.c b/mfshell/commands/mkdir.c
index ba74bd1..07266f3 100644
--- a/mfshell/commands/mkdir.c
+++ b/mfshell/commands/mkdir.c
@@ -34,6 +34,11 @@ int mfshell_cmd_mkdir(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 2) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
diff --git a/mfshell/commands/rmdir.c b/mfshell/commands/rmdir.c
index c616ee3..697d54c 100644
--- a/mfshell/commands/rmdir.c
+++ b/mfshell/commands/rmdir.c
@@ -33,6 +33,11 @@ int mfshell_cmd_rmdir(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 2) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
diff --git a/mfshell/commands/status.c b/mfshell/commands/status.c
index 9aa8cad..0321009 100644
--- a/mfshell/commands/status.c
+++ b/mfshell/commands/status.c
@@ -35,6 +35,11 @@ int mfshell_cmd_status(mfshell * mfshell, int argc, char *const argv[])
     if (mfshell == NULL)
         return -1;
 
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 1) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;
diff --git a/mfshell/commands/whoami.c b/mfshell/commands/whoami.c
index 6e6f3e4..4046e6d 100644
--- a/mfshell/commands/whoami.c
+++ b/mfshell/commands/whoami.c
@@ -29,6 +29,16 @@ int mfshell_cmd_whoami(mfshell * mfshell, int argc, char *const argv[])
     (void)argv;
     int             retval;
 
+    if (mfshell == NULL) {
+        fprintf(stderr, "mfshell is NULL\n");
+        return -1;
+    }
+
+    if (mfshell->conn == NULL) {
+        fprintf(stderr, "conn is NULL\n");
+        return -1;
+    }
+
     if (argc != 1) {
         fprintf(stderr, "Invalid number of arguments\n");
         return -1;