diff --git a/src/basic/missing_loop.h b/src/basic/missing_loop.h
index f83a14c914..56e46f0b8a 100644
--- a/src/basic/missing_loop.h
+++ b/src/basic/missing_loop.h
@@ -26,10 +26,14 @@ assert_cc(LO_FLAGS_DIRECT_IO == 16);
 assert_cc(LOOP_SET_DIRECT_IO == 0x4C08);
 #endif
 
-#ifndef LOOP_SET_STATUS_SETTABLE_FLAGS
-#  define LOOP_SET_STATUS_SETTABLE_FLAGS (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN)
-#endif
-
 #ifndef LOOP_SET_BLOCK_SIZE
 #  define LOOP_SET_BLOCK_SIZE 0x4C09
+#else
+assert_cc(LOOP_SET_BLOCK_SIZE == 0x4C09);
+#endif
+
+#ifndef LOOP_SET_STATUS_SETTABLE_FLAGS
+#  define LOOP_SET_STATUS_SETTABLE_FLAGS (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN)
+#else
+assert_cc(LOOP_SET_STATUS_SETTABLE_FLAGS == (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN));
 #endif