diff --git a/renderdoc/serialise/streamio.cpp b/renderdoc/serialise/streamio.cpp
index 6b073280a..dee9293e1 100644
--- a/renderdoc/serialise/streamio.cpp
+++ b/renderdoc/serialise/streamio.cpp
@@ -281,7 +281,7 @@ bool StreamReader::ReadLargeBuffer(void *buffer, uint64_t length)
     // don't actually read if the destination buffer is NULL
     if(dest)
     {
-      memcpy(dest, m_BufferHead, avail);
+      memcpy(dest, m_BufferHead, (size_t)avail);
       dest += avail;
     }
     length -= avail;
diff --git a/renderdoc/serialise/streamio.h b/renderdoc/serialise/streamio.h
index cfe95335a..79bff33d0 100644
--- a/renderdoc/serialise/streamio.h
+++ b/renderdoc/serialise/streamio.h
@@ -182,7 +182,7 @@ public:
         if(!success)
         {
           if(data)
-            memset(data, 0, numBytes);
+            memset(data, 0, (size_t)numBytes);
           return false;
         }