diff --git a/src/protocols/rdp/guac_rdpdr/rdpdr_fs.c b/src/protocols/rdp/guac_rdpdr/rdpdr_fs.c
index 24a92d37..3b5d2232 100644
--- a/src/protocols/rdp/guac_rdpdr/rdpdr_fs.c
+++ b/src/protocols/rdp/guac_rdpdr/rdpdr_fs.c
@@ -60,11 +60,11 @@ int guac_rdpdr_fs_open(guac_rdpdr_device* device, const char* path) {
 
     /* If no files available, return too many open */
     if (data->open_files >= GUAC_RDPDR_FS_MAX_FILES)
-        return -1;
+        return GUAC_RDPDR_FS_ENFILE;
 
     /* If path is empty, the file does not exist */
     if (path[0] == '\0')
-        return -2;
+        return GUAC_RDPDR_FS_ENOENT;
 
     file->type = GUAC_RDPDR_FS_FILE;
     /* STUB */
diff --git a/src/protocols/rdp/guac_rdpdr/rdpdr_fs.h b/src/protocols/rdp/guac_rdpdr/rdpdr_fs.h
index 8d0073a0..019b6c92 100644
--- a/src/protocols/rdp/guac_rdpdr/rdpdr_fs.h
+++ b/src/protocols/rdp/guac_rdpdr/rdpdr_fs.h
@@ -60,6 +60,16 @@
  */
 #define GUAC_RDPDR_FS_MAX_FILES 128
 
+/**
+ * Error code returned when no more file IDs can be allocated.
+ */
+#define GUAC_RDPDR_FS_ENFILE -1
+
+/**
+ * Error code returned with no such file exists.
+ */
+#define GUAC_RDPDR_FS_ENOENT -2
+
 /*
  * Information constants.
  */
diff --git a/src/protocols/rdp/guac_rdpdr/rdpdr_fs_messages.c b/src/protocols/rdp/guac_rdpdr/rdpdr_fs_messages.c
index 1fadb4b3..2ba5f39d 100644
--- a/src/protocols/rdp/guac_rdpdr/rdpdr_fs_messages.c
+++ b/src/protocols/rdp/guac_rdpdr/rdpdr_fs_messages.c
@@ -89,19 +89,23 @@ void guac_rdpdr_fs_process_create(guac_rdpdr_device* device,
     Stream_Write_UINT32(output_stream, completion_id);
 
     /* If no file IDs available, notify server */
-    if (file_id == -1) {
+    if (file_id == GUAC_RDPDR_FS_ENFILE) {
         guac_client_log_error(device->rdpdr->client, "File open refused - too many open files");
         Stream_Write_UINT32(output_stream, STATUS_TOO_MANY_OPENED_FILES);
         Stream_Write_UINT32(output_stream, 0); /* fileId */
         Stream_Write_UINT8(output_stream,  0); /* information */
     }
-    else if (file_id == -2) {
+
+    /* If file does not exist, notify server */
+    else if (file_id == GUAC_RDPDR_FS_ENOENT) {
         guac_client_log_error(device->rdpdr->client,
                 "File open refused - does not exist: \"%s\"", path);
         Stream_Write_UINT32(output_stream, STATUS_NO_SUCH_FILE);
         Stream_Write_UINT32(output_stream, 0); /* fileId */
         Stream_Write_UINT8(output_stream,  0); /* information */
     }
+
+    /* Otherwise, open succeeded */
     else {
 
         guac_client_log_info(device->rdpdr->client, "Opened file \"%s\" ... new id=%i", path, file_id);