diff --git a/stream/vibe/stream/memory.d b/stream/vibe/stream/memory.d
index b6b9c30e89..6a55fccfbb 100644
--- a/stream/vibe/stream/memory.d
+++ b/stream/vibe/stream/memory.d
@@ -134,7 +134,13 @@ final class MemoryStream : RandomAccessStream {
 	@property bool readable() const nothrow { return true; }
 	@property bool writable() const nothrow { return m_writable; }
 
-	void seek(ulong offset) { assert(offset <= m_size); m_ptr = cast(size_t)offset; }
+	void truncate(ulong size)
+	{
+		enforce(size < m_data.length, "Size limit of memory stream reached.");
+		m_size = cast(size_t)size;
+	}
+
+	void seek(ulong offset) { assert(offset <= m_data.length); m_ptr = cast(size_t)offset; }
 	ulong tell() nothrow { return m_ptr; }
 	const(ubyte)[] peek() { return m_data[m_ptr .. min(m_size, m_ptr+m_peekWindow)]; }