diff --git a/src/lisp/NetBSD-os.c b/src/lisp/NetBSD-os.c
index 5c5a8bf5101567ef75e9490b1432cf53750c366c..76de115d251f8113aa6d9aadfad05e44d3ce6a7d 100644
--- a/src/lisp/NetBSD-os.c
+++ b/src/lisp/NetBSD-os.c
@@ -417,6 +417,7 @@ os_support_sse2()
     int support_sse2;
     size_t len;
 
+    len = sizeof(size_t);
     if (sysctlbyname("machdep.sse2", &support_sse2, &len,
 		     NULL, 0) == 0 && support_sse2 != 0)
 	return TRUE;