diff --git a/src/gcsplugin.cpp b/src/gcsplugin.cpp
index 72ee88d..1e1cb53 100644
--- a/src/gcsplugin.cpp
+++ b/src/gcsplugin.cpp
@@ -242,7 +242,6 @@ void *driver_fopen(const char *filename, char mode)
     ParseGcsUri(filename, bucket_name, object_name);
     FallbackToDefaultBucket(bucket_name);
 	assert(driver_isConnected());
-	assert((mode == 'r' or mode == 'w' or mode == 'a'));
 
     auto h = new MultiPartFile;
     h->bucketname = bucket_name;