diff --git a/libs/microbit/core.cpp b/libs/microbit/core.cpp
index 39a2db37..e4a36350 100644
--- a/libs/microbit/core.cpp
+++ b/libs/microbit/core.cpp
@@ -72,7 +72,7 @@ namespace BooleanMethods {
     bool bang(bool v) { return !v; }
 }
 
-namespace String {
+namespace String_ {
     /**
       * Make a string from the given ASCII character code. 
       */
@@ -129,7 +129,7 @@ namespace NumberImpl {
     int mod(int x, int y) { return x % y; }
 }
 
-namespace Math {
+namespace Math_ {
     /**
       * Returns the value of a base expression taken to a specified power. 
       * @param x The base value of the expression.
@@ -226,22 +226,6 @@ namespace kindscript {
   void *ptrOfLiteral(int offset);
 }
 
-namespace RecordImpl {
-    //%
-    RefRecord* mk(int reflen, int totallen)
-    {
-      check(0 <= reflen && reflen <= totallen, ERR_SIZE, 1);
-      check(reflen <= totallen && totallen <= 255, ERR_SIZE, 2);
-
-      void *ptr = ::operator new(sizeof(RefRecord) + totallen * sizeof(uint32_t));
-      RefRecord *r = new (ptr) RefRecord();
-      r->len = totallen;
-      r->reflen = reflen;
-      memset(r->fields, 0, r->len * sizeof(uint32_t));
-      return r;
-    }
-}
-
 namespace ksrt {
   //%
   uint32_t ldloc(RefLocal *r) {
diff --git a/libs/microbit/core.d.ts b/libs/microbit/core.d.ts
index 07a1492f..916a781c 100644
--- a/libs/microbit/core.d.ts
+++ b/libs/microbit/core.d.ts
@@ -86,7 +86,7 @@ interface String {
   * Converts A string to an integer.
   * @param s A string to convert into a number.
   */
-  //% shim=String::toNumber
+  //% shim=String_::toNumber
 declare function parseInt(s: string): number;
 
 interface Object {}
diff --git a/libs/microbit/shims.d.ts b/libs/microbit/shims.d.ts
index 0852cea2..c48f7dc2 100644
--- a/libs/microbit/shims.d.ts
+++ b/libs/microbit/shims.d.ts
@@ -48,7 +48,7 @@ declare namespace String {
     /**
      * Make a string from the given ASCII character code. 
      */
-    //% shim=String::fromCharCode
+    //% shim=String_::fromCharCode
     function fromCharCode(code: number): string;
 }
 
@@ -67,20 +67,20 @@ declare namespace Math {
      * @param x The base value of the expression.
      * @param y The exponent value of the expression.
      */
-    //% shim=Math::pow
+    //% shim=Math_::pow
     function pow(x: number, y: number): number;
 
     /** 
      * Returns a pseudorandom number between 0 and `max`. 
      */
-    //% shim=Math::random
+    //% shim=Math_::random
     function random(max: number): number;
 
     /**
      * Returns the square root of a number.
      * @param x A numeric expression.
      */
-    //% shim=Math::sqrt
+    //% shim=Math_::sqrt
     function sqrt(x: number): number;
 }