diff --git a/lib/dune b/lib/dune
index 9e7ced6..33e95aa 100644
--- a/lib/dune
+++ b/lib/dune
@@ -8,7 +8,10 @@
    (:standard
     (:include cflags.sexp))))
  (js_of_ocaml
-  (javascript_files runtime.js)))
+  (javascript_files runtime.js))
+ (wasm_of_ocaml
+  (javascript_files runtime.js)
+  (wasm_files runtime.wat)))
 
 (rule
  (targets cflags.sexp)
diff --git a/lib/runtime.wat b/lib/runtime.wat
new file mode 100644
index 0000000..2fdcf55
--- /dev/null
+++ b/lib/runtime.wat
@@ -0,0 +1,38 @@
+(module
+   (import "env" "caml_bigstring_blit_ba_to_ba"
+      (func $bigstringaf_blit_to_bigstring
+         (param (ref eq)) (param (ref eq)) (param (ref eq)) (param (ref eq))
+         (param (ref eq)) (result (ref eq))))
+   (import "env" "caml_bigstring_blit_bytes_to_ba"
+      (func $bigstringaf_blit_from_bytes
+         (param (ref eq)) (param (ref eq)) (param (ref eq)) (param (ref eq))
+         (param (ref eq)) (result (ref eq))))
+   (import "env" "caml_bigstring_blit_ba_to_bytes"
+      (func $bigstringaf_blit_to_bytes
+         (param (ref eq)) (param (ref eq)) (param (ref eq)) (param (ref eq))
+         (param (ref eq)) (result (ref eq))))
+   (import "env" "caml_bigstring_memcmp"
+      (func $bigstringaf_memcmp_bigstring
+         (param (ref eq)) (param (ref eq)) (param (ref eq)) (param (ref eq))
+         (param (ref eq)) (result (ref eq))))
+   (import "env" "caml_bigstring_memcmp_string"
+      (func $bigstringaf_memcmp_string
+         (param (ref eq)) (param (ref eq)) (param (ref eq)) (param (ref eq))
+         (param (ref eq)) (result (ref eq))))
+   (import "env" "caml_bigstring_memchr"
+      (func $caml_bigstring_memchr
+         (param (ref eq)) (param (ref eq)) (param (ref eq)) (param (ref eq))
+         (result (ref eq))))
+
+   (export "bigstringaf_blit_to_bytes" (func $bigstringaf_blit_to_bytes))
+   (export "bigstringaf_blit_to_bigstring" (func $bigstringaf_blit_to_bigstring))
+   (export "bigstringaf_blit_from_bytes" (func $bigstringaf_blit_from_bytes))
+   (export "bigstringaf_memcmp_bigstring" (func $bigstringaf_memcmp_bigstring))
+   (export "bigstringaf_memcmp_string" (func $bigstringaf_memcmp_string))
+
+   (func (export "bigstringaf_memchr")
+      (param $ba (ref eq)) (param $off (ref eq)) (param $chr (ref eq))
+      (param $len (ref eq)) (result (ref eq))
+      (return_call $caml_bigstring_memchr
+         (local.get $ba) (local.get $chr) (local.get $off) (local.get $len)))
+)