diff --git a/common/jpeg/rrutil.h b/common/jpeg/rrutil.h
index 4918120..7ef5cfa 100644
--- a/common/jpeg/rrutil.h
+++ b/common/jpeg/rrutil.h
@@ -47,7 +47,7 @@
 static __inline int numprocs(void)
 {
 	#ifdef _WIN32
-	DWORD ProcAff, SysAff, i;  int count=0;
+	DWORD_PTR ProcAff, SysAff, i; int count=0;
 	if(!GetProcessAffinityMask(GetCurrentProcess(), &ProcAff, &SysAff)) return(1);
 	for(i=0; i<32; i++) if(ProcAff&(1<<i)) count++;
 	return(count);