diff --git a/src/js/trove/dictionary.js b/src/js/trove/dictionary.js
new file mode 100644
index 0000000000..5781a48b7f
--- /dev/null
+++ b/src/js/trove/dictionary.js
@@ -0,0 +1,100 @@
+({
+  requires:
+    [
+      { "import-type": "builtin", name: "valueskeleton" }
+    ],
+  nativeRequires: [],
+  provides: {
+    shorthands: {
+      "dOfAB": ["tyapp", ["local", "StringDict"], [["tid", "a"], ["tid", "b"]]],
+      "Equality": { tag: "name",
+                    origin: { "import-type": "uri", uri: "builtin://equality" },
+                    name: "EqualityResult" },
+      "VS": { tag: "name",
+                    origin: { "import-type": "uri", uri: "builtin://valueskeleton" },
+                    name: "ValueSkeleton" },
+    },
+    values: {
+      "make-dict": ["forall", ["a", "b"], ["arrow", [], "dOfAB"]],
+    },
+    aliases: {
+      "Dict":  {
+        tag: "name",
+        origin: {"import-type": "$ELF"},
+        name: "Dict"
+      }
+    },
+    datatypes: {
+      "Dict": ["data", "Dict", ["a", "b"], [], {
+        "get-now": ["arrow", [["tid", "a"]], ["Option", ["tid", "b"]]],
+        "get-value-now": ["arrow", [["tid", "a"]], ["tid", "b"]],
+        "set-now": ["arrow", [["tid", "a"], ["tid", "b"]], "dOfAB"],
+        "_equals": ["arrow", ["dOfAB", ["arrow", ["Any", "Any"], "Equality"]], "Equality"],
+        "_output":  ["arrow", [["arrow", ["Any"], "VS"]], "VS"],
+      }],
+    }
+  },
+  theModule: function(runtime, namespace, uri, VSlib){
+    var O = runtime.makeObject;
+    var F = runtime.makeFunction;
+    var arity = runtime.checkArity;
+    var get = runtime.getField;
+    var VS = get(VSlib, "values");
+
+    var brandMutable = runtime.namedBrander("dict", ["dict: mutable dict brander"]);
+    var annMutable = runtime.makeBranderAnn(brandMutable, "Dict");
+    var checkMSD = function(v) { runtime._checkAnn(["dict"], annMutable, v); };
+
+    function applyBrand(brand, val) {
+      return get(brand, "brand").app(val);
+    }
+    function hasBrand(brand, val) {
+      return get(brand, "test").app(val);
+    }
+
+    function createDict() {
+      const contents = new Map();
+      var thePyretValue = null;
+      function setNow(key, val) {
+        if(runtime.isRoughnum(key) || runtime.isFunction(key) || runtime.isMethod(key)) {
+          runtime.ffi.throwMessageException("Cannot use roughnum, function, or method as a key in a map");
+        }
+        contents.set(key, val);
+        return thePyretValue;
+      }
+      function getNow(key) {
+        if(contents.has(key)) {
+          return runtime.ffi.makeSome(contents.get(key));
+        }
+        else {
+          return runtime.ffi.makeNone();
+        }
+      }
+      function getValueNow(key) {
+        if(contents.has(key)) {
+          return contents.get(key);
+        }
+        else {
+          runtime.ffi.throwMessageException("Key not found");
+        }
+      }
+      thePyretValue = applyBrand(brandMutable, O({
+        "set-now": F(setNow),
+        "get-now": F(getNow),
+        "get-value-now": F(getValueNow)
+      }));
+      return thePyretValue;
+    }
+
+    var vals = {
+      "make-dict": F(createDict, "make-mutable-string-dict"),
+    };
+    var types = {
+      Dict: annMutable
+    };
+    var internal = {
+      checkMSD: checkMSD
+    };
+    return runtime.makeModuleReturn(vals, types, internal);
+  }
+})
diff --git a/tests/pyret/tests/test-dict.arr b/tests/pyret/tests/test-dict.arr
new file mode 100644
index 0000000000..94ae5fc83d
--- /dev/null
+++ b/tests/pyret/tests/test-dict.arr
@@ -0,0 +1,28 @@
+include dictionary
+
+d = make-dict()
+
+check:
+  d.set-now(5, 1)
+  d.get-value-now(5) is 1
+end
+
+check:
+  d.set-now(0, 1)
+  d.set-now(0, 2)
+  d.get-value-now(0) is 2
+end
+
+check:
+  o = {}
+  o2 = {}
+  d.set-now(o, 1)
+  d.set-now(o2, 3)
+  d.get-value-now(o, 1) is 1
+  d.get-value-now(o2, 3) is 3
+end
+
+check:
+  d.set-now(~4, 100) raises "roughnum"
+  d.set-now(lam(): nothing end, 100) raises "function"
+end