diff --git a/include/dwarfs/options.h b/include/dwarfs/options.h
index 19f7d295..e6fa7b7e 100644
--- a/include/dwarfs/options.h
+++ b/include/dwarfs/options.h
@@ -55,7 +55,7 @@ enum class cache_tidy_strategy { NONE, EXPIRY_TIME, BLOCK_SWAPPED_OUT };
 enum class filesystem_check_level { CHECKSUM, INTEGRITY, FULL };
 
 struct block_cache_options {
-  size_t max_bytes{0};
+  size_t max_bytes{static_cast<size_t>(512) << 20};
   size_t num_workers{0};
   double decompress_ratio{1.0};
   bool mm_release{true};
diff --git a/include/dwarfs/utility/filesystem_extractor.h b/include/dwarfs/utility/filesystem_extractor.h
index 6522844f..88da00ed 100644
--- a/include/dwarfs/utility/filesystem_extractor.h
+++ b/include/dwarfs/utility/filesystem_extractor.h
@@ -43,7 +43,7 @@ class filesystem_v2;
 namespace utility {
 
 struct filesystem_extractor_options {
-  size_t max_queued_bytes{4096};
+  size_t max_queued_bytes{static_cast<size_t>(512) << 20};
   bool continue_on_error{false};
   std::function<void(std::string_view, uint64_t, uint64_t)> progress;
 };