diff --git a/src/babel/transformation/transformers/es7/abstract-references.js b/src/babel/transformation/transformers/es7/abstract-references.js
index 7713b41444..24f82ee750 100644
--- a/src/babel/transformation/transformers/es7/abstract-references.js
+++ b/src/babel/transformation/transformers/es7/abstract-references.js
@@ -24,6 +24,7 @@ var container = function (parent, call, ret, file) {
 export function AssignmentExpression(node, parent, scope, file) {
   var left = node.left;
   if (!t.isVirtualPropertyExpression(left)) return;
+  console.error("Abstract references are deprecated and will be removed in 5.0.0");
 
   var value = node.right;
   var temp;
@@ -65,6 +66,7 @@ export function UnaryExpression(node, parent, scope, file) {
   var arg = node.argument;
   if (!t.isVirtualPropertyExpression(arg)) return;
   if (node.operator !== "delete") return;
+  console.error("Abstract references are deprecated and will be removed in 5.0.0");
 
   var call = util.template("abstract-expression-delete", {
     PROPERTY: arg.property,
@@ -77,6 +79,7 @@ export function UnaryExpression(node, parent, scope, file) {
 export function CallExpression(node, parent, scope) {
   var callee = node.callee;
   if (!t.isVirtualPropertyExpression(callee)) return;
+  console.error("Abstract references are deprecated and will be removed in 5.0.0");
 
   var temp = scope.generateTempBasedOnNode(callee.object);
 
@@ -98,6 +101,7 @@ export function CallExpression(node, parent, scope) {
 }
 
 export function VirtualPropertyExpression(node) {
+  console.error("Abstract references are deprecated and will be removed in 5.0.0");
   return util.template("abstract-expression-get", {
     PROPERTY: node.property,
     OBJECT:   node.object
@@ -105,6 +109,7 @@ export function VirtualPropertyExpression(node) {
 }
 
 export function PrivateDeclaration(node) {
+  console.error("Abstract references are deprecated and will be removed in 5.0.0");
   return t.variableDeclaration("const", node.declarations.map(function (id) {
     return t.variableDeclarator(id, t.newExpression(t.identifier("WeakMap"), []));
   }));
diff --git a/src/babel/transformation/transformers/playground/mallet-operator.js b/src/babel/transformation/transformers/playground/mallet-operator.js
index 25e6896a45..481c7cae36 100644
--- a/src/babel/transformation/transformers/playground/mallet-operator.js
+++ b/src/babel/transformation/transformers/playground/mallet-operator.js
@@ -16,6 +16,7 @@ build(exports, {
   },
 
   build(node) {
+    console.error("The mallet operator is deprecated and will be removed in 5.0.0");
     return t.unaryExpression("!", node, true);
   }
 });
diff --git a/src/babel/transformation/transformers/playground/memoization-operator.js b/src/babel/transformation/transformers/playground/memoization-operator.js
index 7c63ad102a..f8d55d854c 100644
--- a/src/babel/transformation/transformers/playground/memoization-operator.js
+++ b/src/babel/transformation/transformers/playground/memoization-operator.js
@@ -11,6 +11,7 @@ build(exports, {
   },
 
   build(node, file) {
+    console.error("The memoization operator is deprecated and will be removed in 5.0.0");
     return t.unaryExpression(
       "!",
       t.callExpression(