diff --git a/libs/microbit/pins.cpp b/libs/microbit/pins.cpp
index 2c960c88..b2e8b629 100644
--- a/libs/microbit/pins.cpp
+++ b/libs/microbit/pins.cpp
@@ -199,8 +199,8 @@ namespace pins {
     /**
      * Read `size` bytes from a 7-bit I2C `address`.
      */
-    //% repeat.defl=0
-    Buffer i2cReadBuffer(int address, int size, bool repeat)
+    //%
+    Buffer i2cReadBuffer(int address, int size, bool repeat = false)
     {
       Buffer buf = createBuffer(size);
       uBit.i2c.read(address << 1, (char*)buf->payload, size, repeat);
@@ -210,8 +210,8 @@ namespace pins {
     /**
      * Write bytes to a 7-bit I2C `address`.
      */
-    //% repeat.defl=0
-    void i2cWriteBuffer(int address, Buffer buf, bool repeat)
+    //%
+    void i2cWriteBuffer(int address, Buffer buf, bool repeat = false)
     {
       uBit.i2c.write(address << 1, (char*)buf->payload, buf->length, repeat);
     }
diff --git a/libs/microbit/pins.ts b/libs/microbit/pins.ts
index e333bed8..cecc7467 100644
--- a/libs/microbit/pins.ts
+++ b/libs/microbit/pins.ts
@@ -18,7 +18,7 @@ namespace pins {
      * Read one number from 7-bit I2C address.
      */
     export function i2cReadNumber(address: number, format: NumberFormat): number {
-        let buf = pins.i2cReadBuffer(address, pins.sizeOf(format), false)
+        let buf = pins.i2cReadBuffer(address, pins.sizeOf(format))
         return buf.getNumber(format, 0)
     }
 
@@ -28,7 +28,7 @@ namespace pins {
     export function i2cWriteNumber(address: number, value: number, format: NumberFormat): void {
         let buf = createBuffer(pins.sizeOf(format))
         buf.setNumber(format, 0, value)
-        pins.i2cWriteBuffer(address, buf, false)
+        pins.i2cWriteBuffer(address, buf)
     }
 
     /**
diff --git a/libs/microbit/shims.d.ts b/libs/microbit/shims.d.ts
index f9cae3aa..2acbac00 100644
--- a/libs/microbit/shims.d.ts
+++ b/libs/microbit/shims.d.ts
@@ -375,7 +375,7 @@ declare namespace control {
      */
     //% weight=21 blockGap=12 blockId="control_raise_event" block="raise event|from source %src=control_event_source|with value %value=control_event_value" blockExternalInputs=1
     //% mode.defl=1 shim=control::raiseEvent
-    function raiseEvent(src: number, value: number, mode: EventCreationMode): void;
+    function raiseEvent(src: number, value: number, mode?: EventCreationMode): void;
 
     /**
      * Raises an event in the event bus.
@@ -546,13 +546,13 @@ declare namespace pins {
      * Read `size` bytes from a 7-bit I2C `address`.
      */
     //% repeat.defl=0 shim=pins::i2cReadBuffer
-    function i2cReadBuffer(address: number, size: number, repeat: boolean): Buffer;
+    function i2cReadBuffer(address: number, size: number, repeat?: boolean): Buffer;
 
     /**
      * Write bytes to a 7-bit I2C `address`.
      */
     //% repeat.defl=0 shim=pins::i2cWriteBuffer
-    function i2cWriteBuffer(address: number, buf: Buffer, repeat: boolean): void;
+    function i2cWriteBuffer(address: number, buf: Buffer, repeat?: boolean): void;
 }