diff --git a/microbit/src/03-setup/.cargo/config b/microbit/src/03-setup/.cargo/config.toml
similarity index 100%
rename from microbit/src/03-setup/.cargo/config
rename to microbit/src/03-setup/.cargo/config.toml
diff --git a/microbit/src/05-led-roulette/.cargo/config b/microbit/src/05-led-roulette/.cargo/config.toml
similarity index 100%
rename from microbit/src/05-led-roulette/.cargo/config
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diff --git a/microbit/src/07-uart/.cargo/config b/microbit/src/07-uart/.cargo/config.toml
similarity index 100%
rename from microbit/src/07-uart/.cargo/config
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diff --git a/microbit/src/08-i2c/.cargo/config b/microbit/src/08-i2c/.cargo/config.toml
similarity index 100%
rename from microbit/src/08-i2c/.cargo/config
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diff --git a/microbit/src/09-led-compass/.cargo/config b/microbit/src/09-led-compass/.cargo/config.toml
similarity index 100%
rename from microbit/src/09-led-compass/.cargo/config
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diff --git a/microbit/src/10-punch-o-meter/.cargo/config b/microbit/src/10-punch-o-meter/.cargo/config.toml
similarity index 100%
rename from microbit/src/10-punch-o-meter/.cargo/config
rename to microbit/src/10-punch-o-meter/.cargo/config.toml
diff --git a/microbit/src/11-snake-game/.cargo/config b/microbit/src/11-snake-game/.cargo/config.toml
similarity index 100%
rename from microbit/src/11-snake-game/.cargo/config
rename to microbit/src/11-snake-game/.cargo/config.toml