diff --git a/Sources/Plasma/PubUtilLib/plFile/plSecureStream.cpp b/Sources/Plasma/PubUtilLib/plFile/plSecureStream.cpp
index e4f4e3ec..2c0279f2 100644
--- a/Sources/Plasma/PubUtilLib/plFile/plSecureStream.cpp
+++ b/Sources/Plasma/PubUtilLib/plFile/plSecureStream.cpp
@@ -602,7 +602,8 @@ bool plSecureStream::ICheckMagicString(hsFD fp)
 {
     char magicString[kMagicStringLen+1];
 #ifdef HS_BUILD_FOR_WIN32
-    ReadFile(fp, &magicString, kMagicStringLen, NULL, NULL);
+    DWORD numread;
+    ReadFile(fp, &magicString, kMagicStringLen, &numread, NULL);
 #elif HS_BUILD_FOR_UNIX
     fread(&magicString, kMagicStringLen, 1, fp);
 #endif