diff --git a/src/basic/missing_loop.h b/src/basic/missing_loop.h
index b88501d78b..f83a14c914 100644
--- a/src/basic/missing_loop.h
+++ b/src/basic/missing_loop.h
@@ -29,3 +29,7 @@ assert_cc(LOOP_SET_DIRECT_IO == 0x4C08);
 #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
+#endif