diff --git a/karma.conf.js b/karma.conf.js
index 744a7ca..f2bbf72 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -23,8 +23,8 @@ module.exports = function (config) {
     ],
     customLaunchers: {
       chromeDebugging: {
-        base: 'Chrome',
-        flags: [ '--remote-debugging-port=9333' ]
+        base: "Chrome",
+        flags: [ "--remote-debugging-port=9333" ]
       },
       chromeTravisCi: {
         base: "Chrome",
diff --git a/package-lock.json b/package-lock.json
index a2040d4..eb9f8cd 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "dice-typescript",
-  "version": "1.4.1",
+  "version": "1.5.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -1486,7 +1486,8 @@
         "ansi-regex": {
           "version": "2.1.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "aproba": {
           "version": "1.1.1",
@@ -1561,6 +1562,7 @@
           "version": "2.10.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "hoek": "2.16.3"
           }
@@ -1730,6 +1732,7 @@
           "version": "1.0.11",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "graceful-fs": "4.1.11",
             "inherits": "2.0.3",
@@ -1797,7 +1800,8 @@
         "graceful-fs": {
           "version": "4.1.11",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "har-schema": {
           "version": "1.0.5",
@@ -1984,12 +1988,14 @@
         "minimist": {
           "version": "0.0.8",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "mkdirp": {
           "version": "0.5.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "minimist": "0.0.8"
           }
@@ -2279,6 +2285,7 @@
           "version": "3.0.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "ansi-regex": "2.1.1"
           }
@@ -4978,4 +4985,4 @@
       "dev": true
     }
   }
-}
\ No newline at end of file
+}
diff --git a/package.json b/package.json
index 8e10833..211ba64 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "dice-typescript",
-  "version": "1.5.0",
+  "version": "1.6.0",
   "description": "A TypeScript library for parsing dice rolling expressions, most commonly used in tabletop RPGs.",
   "main": "./dist/index.js",
   "scripts": {
diff --git a/spec/generator/dice-generator.generate.drop.spec.ts b/spec/generator/dice-generator.generate.drop.spec.ts
index 28dba13..40988ef 100644
--- a/spec/generator/dice-generator.generate.drop.spec.ts
+++ b/spec/generator/dice-generator.generate.drop.spec.ts
@@ -29,5 +29,19 @@ describe('DiceGenerator', () => {
       const generator = new Generator.DiceGenerator();
       expect(generator.generate(exp)).toBe('2d6dh');
     });
+    it('generates a drop with modifier (3d6dh2).', () => {
+      const exp = Ast.Factory.create(Ast.NodeType.Drop)
+        .setAttribute('type', 'highest');
+
+      const dice = Ast.Factory.create(Ast.NodeType.Dice);
+      dice.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 3));
+      dice.addChild(Ast.Factory.create(Ast.NodeType.DiceSides).setAttribute('value', 6));
+
+      exp.addChild(dice);
+      exp.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 2));
+
+      const generator = new Generator.DiceGenerator();
+      expect(generator.generate(exp)).toBe('3d6dh2');
+    });
   });
 });
diff --git a/spec/generator/dice-generator.generate.keep.spec.ts b/spec/generator/dice-generator.generate.keep.spec.ts
index 1de295b..b03f4d3 100644
--- a/spec/generator/dice-generator.generate.keep.spec.ts
+++ b/spec/generator/dice-generator.generate.keep.spec.ts
@@ -29,5 +29,19 @@ describe('DiceGenerator', () => {
       const generator = new Generator.DiceGenerator();
       expect(generator.generate(exp)).toBe('2d6kl');
     });
+    it('generates a keep with modifier (3d6kl2).', () => {
+      const exp = Ast.Factory.create(Ast.NodeType.Keep)
+        .setAttribute('type', 'lowest');
+
+      const dice = Ast.Factory.create(Ast.NodeType.Dice);
+      dice.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 3));
+      dice.addChild(Ast.Factory.create(Ast.NodeType.DiceSides).setAttribute('value', 6));
+
+      exp.addChild(dice);
+      exp.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 2));
+
+      const generator = new Generator.DiceGenerator();
+      expect(generator.generate(exp)).toBe('3d6kl2');
+    });
   });
 });
diff --git a/spec/interpreter/dice-interpreter.interpret.simple.ts b/spec/interpreter/dice-interpreter.interpret.simple.ts
index 5513d05..7eac53d 100644
--- a/spec/interpreter/dice-interpreter.interpret.simple.ts
+++ b/spec/interpreter/dice-interpreter.interpret.simple.ts
@@ -24,5 +24,26 @@ describe('DiceInterpreter', () => {
       expect(res.renderedExpression).toBe('[1, 7, 4, 5] + 5', 'Expression rendered incorrectly');
       expect(res.total).toBe(22, 'Total counted incorrectly');
     });
+    it('interprets a simple dice expression (4d6kh3).', () => {
+      const exp = Ast.Factory.create(Ast.NodeType.Keep)
+        .setAttribute('type', 'highest');
+
+      const dice = Ast.Factory.create(Ast.NodeType.Dice);
+      dice.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 4));
+      dice.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 6));
+
+      exp.addChild(dice);
+      exp.addChild(Ast.Factory.create(Ast.NodeType.Number).setAttribute('value', 3));
+
+      const mockList = new MockListRandomProvider();
+      mockList.numbers.push(6, 1, 4, 3);
+
+      const interpreter = new Interpreter.DiceInterpreter(null, mockList);
+      const res = interpreter.interpret(exp);
+
+      expect(res.errors.length).toBe(0, 'Unexpected errors found.');
+      expect(res.renderedExpression).toBe('[6, 1, 4, 3]kh3', 'Expression rendered incorrectly');
+      expect(res.total).toBe(13, 'Total counted incorrectly');
+    });
   });
 });
diff --git a/src/generator/dice-generator.class.ts b/src/generator/dice-generator.class.ts
index a172bbb..655f4f0 100644
--- a/src/generator/dice-generator.class.ts
+++ b/src/generator/dice-generator.class.ts
@@ -134,18 +134,22 @@ export class DiceGenerator implements Generator<string> {
 
   generateKeep(expression: Ast.ExpressionNode): string {
     this.expectChildCount(expression, 1);
-    let keep = 'k';
-    if (expression.getAttribute('type') === 'highest') { keep += 'h'; }
-    if (expression.getAttribute('type') === 'lowest') { keep += 'l'; }
-    return this.generate(expression.getChild(0)) + keep;
+    let exp = 'k';
+    if (expression.getAttribute('type') === 'highest') { exp += 'h'; }
+    if (expression.getAttribute('type') === 'lowest') { exp += 'l'; }
+
+    if (expression.getChildCount() > 1) { exp += this.generate(expression.getChild(1)); }
+    return this.generate(expression.getChild(0)) + exp;
   }
 
   generateDrop(expression: Ast.ExpressionNode): string {
     this.expectChildCount(expression, 1);
-    let drop = 'd';
-    if (expression.getAttribute('type') === 'highest') { drop += 'h'; }
-    if (expression.getAttribute('type') === 'lowest') { drop += 'l'; }
-    return this.generate(expression.getChild(0)) + drop;
+    let exp = 'd';
+    if (expression.getAttribute('type') === 'highest') { exp += 'h'; }
+    if (expression.getAttribute('type') === 'lowest') { exp += 'l'; }
+
+    if (expression.getChildCount() > 1) { exp += this.generate(expression.getChild(1)); }
+    return this.generate(expression.getChild(0)) + exp;
   }
 
   generateCritical(expression: Ast.ExpressionNode): string {