diff --git a/source/mijin/io/stream.cpp b/source/mijin/io/stream.cpp
index 284c897..b7d04c5 100644
--- a/source/mijin/io/stream.cpp
+++ b/source/mijin/io/stream.cpp
@@ -282,7 +282,7 @@ StreamError MemoryStream::seek(std::intptr_t pos, SeekMode seekMode)
             newPos = static_cast<std::intptr_t>(data_.size()) + pos;
             break;
     }
-    if (newPos < 0 || newPos > data_.size()) {
+    if (newPos < 0 || newPos > static_cast<std::intptr_t>(data_.size())) {
         return StreamError::IO_ERROR;
     }
     pos_ = newPos;