diff --git a/tests/rx2c.py b/tests/rx2c.py
index 7cd8c4c..f602728 100644
--- a/tests/rx2c.py
+++ b/tests/rx2c.py
@@ -479,8 +479,8 @@ def writeProlog(file):
                 "	data = DRAM_READ(mmu);\n"
                 "	mmu->m0 += 8;\n"
                 "	mmu->mx ^= addr;\n"
-                "	if((mmu->mx & 0xFFFF) == 0) {\n"
-                "		mmu->m0 = mmu->mx;\n"
+                "	if((mmu->mx & 0xFFF8) == 0) {\n"
+                "		mmu->m0 = mmu->mx & ~7U;\n"
                 "#if defined(PREF)\n"
                 "		PREFETCH(mmu);\n"
                 "#endif\n"