diff --git a/src/lib-sieve/storage/file/sieve-file-storage.c b/src/lib-sieve/storage/file/sieve-file-storage.c
index 15a2183df63424e8a66198482079ddbfc7483e2f..ee914b1df38ea86a9b81619da8405967f879b6ad 100644
--- a/src/lib-sieve/storage/file/sieve-file-storage.c
+++ b/src/lib-sieve/storage/file/sieve-file-storage.c
@@ -377,6 +377,8 @@ static int sieve_file_storage_init_common
 		storage_path = active_path;
 	}
 
+	i_assert(storage_path != NULL);
+
 	/* Prepare for write access */
 
 	if ( (storage->flags & SIEVE_STORAGE_FLAG_READWRITE) != 0 ) {