diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 1dc8a74bc3..da619e764c 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -42,10 +42,10 @@ const (
 )
 
 var (
-	blockCacheMaxItems     = 32768                  // Maximum number of blocks to cache before throttling the download
-	blockCacheInitialItems = 2048                   // Initial number of blocks to start fetching, before we know the sizes of the blocks
-	blockCacheMemory       = 2 * 1024 * 1024 * 1024 // Maximum amount of memory to use for block caching
-	blockCacheSizeWeight   = 0.1                    // Multiplier to approximate the average block size based on past ones
+	blockCacheMaxItems            = 32768                  // Maximum number of blocks to cache before throttling the download
+	blockCacheInitialItems        = 2048                   // Initial number of blocks to start fetching, before we know the sizes of the blocks
+	blockCacheSizeWeight          = 0.1                    // Multiplier to approximate the average block size based on past ones
+	blockCacheMemory       uint64 = 2 * 1024 * 1024 * 1024 // Maximum amount of memory to use for block caching
 )
 
 var (