diff --git a/netwerk/cache2/CacheFileMetadata.cpp b/netwerk/cache2/CacheFileMetadata.cpp
index 91216b308a6..dc49137ada2 100644
--- a/netwerk/cache2/CacheFileMetadata.cpp
+++ b/netwerk/cache2/CacheFileMetadata.cpp
@@ -185,11 +185,17 @@ CacheFileMetadata::ReadMetadata(CacheFileMetadataListener *aListener)
     return NS_OK;
   }
 
-  // round offset to 4k blocks
-  int64_t offset = (size / kAlignSize) * kAlignSize;
+  // Set offset so that we read at least kMinMetadataRead if the file is big
+  // enough.
+  int64_t offset;
+  if (size < kMinMetadataRead) {
+    offset = 0;
+  } else {
+    offset = size - kMinMetadataRead;
+  }
 
-  if (size - offset < kMinMetadataRead && offset > kAlignSize)
-    offset -= kAlignSize;
+  // round offset to kAlignSize blocks
+  offset = (offset / kAlignSize) * kAlignSize;
 
   mBufSize = size - offset;
   mBuf = static_cast<char *>(moz_xmalloc(mBufSize));