diff --git a/tools/jsc/include/thinthin.h b/tools/jsc/include/thinthin.h
new file mode 100644
index 00000000..c3f43ccc
--- /dev/null
+++ b/tools/jsc/include/thinthin.h
@@ -0,0 +1,16 @@
+#define thinthin_tablesize_default 65536
+#define thinthin_memsize_default (128 * 1024 * 1024LL)
+#define thinthin_stacksize_default (1 * 1024 * 1024LL)
+#define thinthin_stackbot_default (thinthin_memsize_default - thinthin_stacksize_default)
+
+const struct {
+  long long tablesize;
+  long long memsize;
+  long long stacksize;
+  long long stackbottom;
+} default_sizes = {
+  thinthin_tablesize_default,
+  thinthin_memsize_default,
+  thinthin_stacksize_default,
+  thinthin_stackbot_default,
+};