diff --git a/can-define.js b/can-define.js
index 1082858..9098a53 100644
--- a/can-define.js
+++ b/can-define.js
@@ -182,6 +182,17 @@ define.property = function(objPrototype, prop, definition, dataInitializers, com
 
 	var type = definition.type;
 
+	//!steal-remove-start
+	if (type && canReflect.isConstructorLike(type)) {
+		dev.warn(
+			"can-define: the definition for " +
+			prop +
+			(objPrototype.constructor.shortName ? " on " + objPrototype.constructor.shortName : "") +
+			" uses a constructor for \"type\". Did you mean \"Type\"?"
+		);
+	}
+	//!steal-remove-end
+
 	// Special case definitions that have only `type: "*"`.
 	if (type && onlyType(definition) && type === define.types["*"]) {
 		Object.defineProperty(objPrototype, prop, {
diff --git a/define-test.js b/define-test.js
index 2d94fc4..e04de66 100644
--- a/define-test.js
+++ b/define-test.js
@@ -5,6 +5,7 @@ var CanList = require("can-define/list/list");
 var canBatch = require("can-event/batch/batch");
 var each = require("can-util/js/each/each");
 var canSymbol = require("can-symbol");
+var canDev = require("can-util/js/dev/dev");
 
 QUnit.module("can-define");
 
@@ -1368,3 +1369,45 @@ QUnit.test('define() should add a CID (#246)', function() {
 	var g = new Greeting();
 	QUnit.ok(g._cid, "should have a CID property");
 });
+
+if (System.env.indexOf("production") < 0) {
+
+	QUnit.test("warn on using a Constructor for small-t type definintions", function() {
+		expect(2);
+		var oldWarn = canDev.warn;
+		canDev.warn = function(mesg) {
+			QUnit.equal(mesg, "can-define: the definition for currency uses a constructor for \"type\". Did you mean \"Type\"?");
+		};
+
+		function Currency() {
+			return this;
+		}
+		Currency.prototype = {
+			symbol: "USD"
+		};
+
+		function VM() {}
+		define(VM.prototype, {
+		    currency: {
+		        type: Currency, // should be `Type: Currency`
+		        value: new Currency({})
+		    }
+		});
+
+		canDev.warn = function(mesg) {
+			QUnit.equal(mesg, "can-define: the definition for currency on VM2 uses a constructor for \"type\". Did you mean \"Type\"?");
+		};
+
+		function VM2() {}
+		VM2.shortName = "VM2";
+		define(VM2.prototype, {
+		    currency: {
+		        type: Currency, // should be `Type: Currency`
+		        value: new Currency({})
+		    }
+		});
+
+		canDev.warn = oldWarn;
+	});
+
+}
\ No newline at end of file