diff --git a/Source/Core/DiscIO/WbfsBlob.cpp b/Source/Core/DiscIO/WbfsBlob.cpp
index 33c4c90b53..7aaa09c8b1 100644
--- a/Source/Core/DiscIO/WbfsBlob.cpp
+++ b/Source/Core/DiscIO/WbfsBlob.cpp
@@ -51,6 +51,11 @@ WbfsFileReader::~WbfsFileReader()
 	delete[] m_wlba_table;
 }
 
+u64 WbfsFileReader::GetDataSize() const
+{
+	return WII_SECTOR_COUNT * WII_SECTOR_SIZE;
+}
+
 bool WbfsFileReader::OpenFiles(const std::string& filename)
 {
 	m_total_files = 0;
diff --git a/Source/Core/DiscIO/WbfsBlob.h b/Source/Core/DiscIO/WbfsBlob.h
index d090ad461c..ce9d42953e 100644
--- a/Source/Core/DiscIO/WbfsBlob.h
+++ b/Source/Core/DiscIO/WbfsBlob.h
@@ -20,7 +20,12 @@ public:
 	static WbfsFileReader* Create(const std::string& filename);
 
 	BlobType GetBlobType() const override { return BlobType::WBFS; }
-	u64 GetDataSize() const override { return m_size; }
+
+	// The WBFS format does not save the original file size.
+	// This function returns a constant upper bound
+	// (the size of a double-layer Wii disc).
+	u64 GetDataSize() const override;
+
 	u64 GetRawSize() const override { return m_size; }
 	bool Read(u64 offset, u64 nbytes, u8* out_ptr) override;