diff --git a/testsuite/tests/cmm/should_run/machops/T20638.cmm b/testsuite/tests/cmm/should_run/machops/T20638.cmm
index 51fe449a767bd74e75c8c77c20c40c7628d850e8..64835b7584aa7bba841d3f455b2a2699a5496c86 100644
--- a/testsuite/tests/cmm/should_run/machops/T20638.cmm
+++ b/testsuite/tests/cmm/should_run/machops/T20638.cmm
@@ -1,4 +1,4 @@
 test(bits64 buffer) {
-  return (%zx64(%shrl(bits16[buffer + (128 :: bits64)], (1 :: bits64))) & (64711 :: bits64));
+  return (%zx64(%shrl(bits16[buffer + (128 :: bits64)], (1 :: bits64))) & (65407 :: bits64));
 }
 
diff --git a/testsuite/tests/cmm/should_run/machops/T20638.stdout b/testsuite/tests/cmm/should_run/machops/T20638.stdout
index 5a54842902527d6f004ccdde6c237a356c953be1..81669a3724732c41909ffa589f0f918f937d88f4 100644
--- a/testsuite/tests/cmm/should_run/machops/T20638.stdout
+++ b/testsuite/tests/cmm/should_run/machops/T20638.stdout
@@ -1 +1 @@
-16576
+16448