diff --git a/shlr/heap/include/r_jemalloc/internal/jemalloc_internal.h b/shlr/heap/include/r_jemalloc/internal/jemalloc_internal.h
index e3b601bb31..461289d044 100644
--- a/shlr/heap/include/r_jemalloc/internal/jemalloc_internal.h
+++ b/shlr/heap/include/r_jemalloc/internal/jemalloc_internal.h
@@ -256,6 +256,9 @@ typedef unsigned szind_t;
 #  ifdef __hppa__
 #    define LG_QUANTUM		4
 #  endif
+#  ifdef __m68k__
+#    define LG_QUANTUM          3
+#  endif
 #  ifdef __mips__
 #    define LG_QUANTUM		3
 #  endif