diff --git a/src/modules/filesystem/file.c b/src/modules/filesystem/file.c
index e5e5a839..72de0213 100644
--- a/src/modules/filesystem/file.c
+++ b/src/modules/filesystem/file.c
@@ -41,7 +41,7 @@ size_t lovrFileRead(File* file, void* data, size_t bytes) {
 }
 
 size_t lovrFileWrite(File* file, const void* data, size_t bytes) {
-  lovrAssert(file->handle && (file->mode == OPEN_READ || file->mode == OPEN_WRITE), "File must be open for writing");
+  lovrAssert(file->handle && (file->mode == OPEN_WRITE || file->mode == OPEN_APPEND), "File must be open for writing");
   return PHYSFS_writeBytes(file->handle, data, bytes);
 }