I having some trouble running the Flipper example from the Ink! webpage.

The cargo contract build outputs the following error log:

ERROR: Loading of original wasm failed

Caused by:
    0: Loading of wasm module at '/Users/winston/workspace/cs/repos/flipper/target/ink/wasm32-unknown-unknown/release/flipper.wasm' failed
    1: Unknown opcode 192

rustup show output:

Default host: aarch64-apple-darwin
rustup home:  /Users/winston/.rustup

installed toolchains

nightly-aarch64-apple-darwin (default)

installed targets for active toolchain


active toolchain

nightly-aarch64-apple-darwin (default)
rustc 1.70.0-nightly (17c116721 2023-03-29)

As you can see, I am running on the M1 OSX system.

  • 1
    Please, remember to mark this question as solved :) Mar 30 at 17:02

2 Answers 2


Solved! This was caused by the nightly toolchain. Switching to the stable toolchain solved this issue.

Edit: As pointed out by Shunsuke, this is specific to the 1.70.0 nightly build. 1.68.0 version seems to work.

  • 1
    Lots of contracts including OpenBrush PSP22, PSP34 contracts using nightly features such as #![feature(min_specialization)]. This means existing contracts cannot be compiled with nightly toolchain whose rustc version is higher than 1.70.0 (Confirmed 1.68.0 works). cargo contract is now independent from nightly toolchain but it should still support nightly for compatibility.
    – Shunsuke
    Mar 31 at 7:41
  • 2

For cases where updated nightly is still preferred for whatever reason:

rustup update
rustup install nightly-2023-02-07-aarch64-apple-darwin
rustup component add rust-src --toolchain nightly-2023-02-07-aarch64-apple-darwin

...specify nightly version in tag

cargo +nightly-2023-02-07 contract build

Still running updated nightly rustc 1.70.0 as default: image

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