diff --git a/libs/microbit/serial.cpp b/libs/microbit/serial.cpp
index b3aa6a8c..bdd15adb 100644
--- a/libs/microbit/serial.cpp
+++ b/libs/microbit/serial.cpp
@@ -15,7 +15,7 @@ namespace serial {
     /**
      * Sends a piece of text through Serial connection.
      */
-    //%
+    //% blockId=serial_writestring block="serial write %text"
     void writeString(StringData *text) { 
       uBit.serial.send(ManagedString(text));
     }
diff --git a/libs/microbit/serial.ts b/libs/microbit/serial.ts
index 326c7369..0649cded 100644
--- a/libs/microbit/serial.ts
+++ b/libs/microbit/serial.ts
@@ -8,7 +8,7 @@ namespace serial {
      * @param value to send over serial
      */
     //% help=serial/write-line
-    //% blockId=serial_writeline block="serial|write %text"
+    //% blockId=serial_writeline block="serial|write line %text"
     export function writeLine(text: string): void {
         writeString(text);
         writeString("\r\n");
@@ -17,6 +17,7 @@ namespace serial {
     /**
      * Prints a numeric value to the serial
      */
+    //% blockId=serial_writenumber block="serial|write number %value"
     export function writeNumber(value: number): void {
         writeString(value.toString());
     }
diff --git a/libs/microbit/shims.d.ts b/libs/microbit/shims.d.ts
index 4f60205a..7c8abbb3 100644
--- a/libs/microbit/shims.d.ts
+++ b/libs/microbit/shims.d.ts
@@ -528,7 +528,7 @@ declare namespace serial {
     /**
      * Sends a piece of text through Serial connection.
      */
-    //% shim=serial::writeString
+    //% blockId=serial_writestring block="serial write %text" shim=serial::writeString
     function writeString(text: string): void;
 }
 
diff --git a/package.json b/package.json
index f12e5a8f..cab56e15 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pxt-microbit",
-  "version": "0.2.90",
+  "version": "0.2.91",
   "description": "BBC micro:bit target for PXT",
   "keywords": [
     "JavaScript",
@@ -29,6 +29,6 @@
     "typescript": "^1.8.7"
   },
   "dependencies": {
-    "pxt-core": "0.2.98"
+    "pxt-core": "0.2.99"
   }
 }