diff --git a/make_wasm.py b/make_wasm.py
index deac9c7..d4e4b0c 100755
--- a/make_wasm.py
+++ b/make_wasm.py
@@ -1,7 +1,8 @@
 #! /usr/bin/env python3
 
 from argparse import ArgumentParser
-from subprocess import call
+from subprocess import check_call
+from shutil import copyfile
 
 if __name__ == "__main__":
     parser = ArgumentParser(description="Build js and wasm")
@@ -11,13 +12,22 @@ if __name__ == "__main__":
     args = parser.parse_args()
 
     if args.release:
-        call(["cargo", "build", "--release",
-              "--target", "wasm32-unknown-unknown"])
+        check_call(["cargo", "build", "--release",
+                    "--target", "wasm32-unknown-unknown"])
         target = "target/wasm32-unknown-unknown/release/webgl.wasm"
     else:
-        call(["cargo", "build",
-              "--target", "wasm32-unknown-unknown"])
+        check_call(["cargo", "build",
+                    "--target", "wasm32-unknown-unknown"])
         target = "target/wasm32-unknown-unknown/debug/webgl.wasm"
 
-    call(["wasm-bindgen", target, "--out-dir", ".",
-          "--no-typescript", "--target", "web"])
+    check_call(["wasm-bindgen", target, "--out-dir", ".",
+                "--no-typescript", "--target", "web"])
+
+    if args.release:
+        try:
+            copyfile("webgl_bg.wasm", "before-wasm-opt.wasm")
+            check_call(["wasm-opt", "-O4", "before-wasm-opt.wasm",
+                        "-o", "webgl_bg.wasm"])
+        except FileNotFoundError:
+            print("wasm-opt not found, not optimising further")
+            pass