diff --git a/pxtcompiler/emitter/emitter.ts b/pxtcompiler/emitter/emitter.ts
index d90a671c02f6..462faf1728f9 100644
--- a/pxtcompiler/emitter/emitter.ts
+++ b/pxtcompiler/emitter/emitter.ts
@@ -1914,7 +1914,14 @@ ${lbl}: .short 0xffff
                     return emitCallCore(node, node, [], null, decl as any, node.expression)
                 } else {
                     let idx = fieldIndex(node)
-                    return ir.op(EK.FieldAccess, [emitExpr(node.expression)], idx)
+                    const fld = getFieldInfo(idx.classInfo, idx.name)
+                    const attrs = parseComments(fld);
+                    if (attrs.shim) {
+                        // Reading a shimmed property
+                        return emitShim(fld, decl, [node.expression])
+                    } else {
+                        return ir.op(EK.FieldAccess, [emitExpr(node.expression)], idx)
+                    }
                 }
             } else if (isClassFunction(decl) || decl.kind == SK.MethodSignature) {
                 // TODO this is now supported in runtime; can be probably relaxed (by using GetAccessor code path above)
@@ -2124,10 +2131,10 @@ ${lbl}: .short 0xffff
             return m
         }
 
-        function emitShim(decl: Declaration, node: Node, args: Expression[]): ir.Expr {
+        function emitShim(decl: Declaration, node: Node, args: Expression[], shimOverride: string = null): ir.Expr {
             let attrs = parseComments(decl)
             let hasRet = !(typeOf(node).flags & TypeFlags.Void)
-            let nm = attrs.shim
+            let nm = shimOverride || attrs.shim
 
             if (nm.indexOf('(') >= 0) {
                 let parse = /(.*)\((.*)\)$/.exec(nm)
@@ -2421,7 +2428,12 @@ ${lbl}: .short 0xffff
                 }
 
                 if (attrs.shim && !hasShimDummy(decl)) {
-                    return emitShim(decl, node, args);
+                    let shimOverride: string = undefined;
+                    if (node.kind === SK.PropertyAccessExpression && args.length > 1) {
+                        // Assigning a value to a shimmed property, append "_set" to the shim name.
+                        shimOverride = attrs.shim + "_set";
+                    }
+                    return emitShim(decl, node, args, shimOverride);
                 } else if (attrs.helper) {
                     let syms = checker.getSymbolsInScope(node, SymbolFlags.Module)
                     let helperStmt: Statement
@@ -3329,8 +3341,21 @@ ${lbl}: .short 0xffff
                 } else if (decl && (decl.kind == SK.PropertySignature || decl.kind == SK.PropertyAssignment || isSlowField(decl))) {
                     proc.emitExpr(emitCallCore(trg, trg, [src], null, decl as FunctionLikeDeclaration))
                 } else {
-                    let trg2 = emitExpr(trg)
-                    proc.emitExpr(ir.op(EK.Store, [trg2, emitExpr(src)]))
+                    for (;;) {
+                        if (trg.kind == SK.PropertyAccessExpression) {
+                            const idx = fieldIndex(trg as PropertyAccessExpression)
+                            const fld = getFieldInfo(idx.classInfo, idx.name)
+                            const attrs = parseComments(fld);
+                            if (attrs.shim) {
+                                // Reading a shimmed property
+                                proc.emitExpr(emitCallCore(trg, trg, [src], null, decl as FunctionLikeDeclaration))
+                                break;
+                            }
+                        }
+                        let trg2 = emitExpr(trg)
+                        proc.emitExpr(ir.op(EK.Store, [trg2, emitExpr(src)]))
+                        break;
+                    }
                 }
             } else if (trg.kind == SK.ElementAccessExpression) {
                 proc.emitExpr(emitIndexedAccess(trg as ElementAccessExpression, src))