diff --git a/src/components/fields/FunctionSpecField.jsx b/src/components/fields/FunctionSpecField.jsx
index a6920442..b0c0afc6 100644
--- a/src/components/fields/FunctionSpecField.jsx
+++ b/src/components/fields/FunctionSpecField.jsx
@@ -22,7 +22,7 @@ function isDataField(value) {
  * properties accept arrays as values, for example `text-font`. So we must try
  * and create an expression.
  */
-function isExpression(value, fieldSpec={}) {
+function checkIsExpression (value, fieldSpec={}) {
   if (!Array.isArray(value)) {
     return false;
   }
@@ -72,6 +72,13 @@ export default class FunctionSpecProperty  extends React.Component {
     ]),
   }
 
+  constructor (props) {
+    super();
+    this.state = {
+      isExpression: checkIsExpression(props.value, props.fieldSpec),
+    }
+  }
+
   getFieldFunctionType(fieldSpec) {
     if (fieldSpec.expression.interpolated) {
       return "exponential"
@@ -103,6 +110,13 @@ export default class FunctionSpecProperty  extends React.Component {
     this.props.onChange(this.props.fieldName, changedValue)
   }
 
+  deleteExpression = (newValue) => {
+    this.props.onChange(this.props.fieldName, newValue);
+    this.setState({
+      isExpression: false,
+    });
+  }
+
   deleteStop = (stopIdx) => {
     const stops = this.props.value.stops.slice(0)
     stops.splice(stopIdx, 1)
@@ -132,6 +146,10 @@ export default class FunctionSpecProperty  extends React.Component {
   makeExpression = () => {
     const expression = ["literal", this.props.value || this.props.fieldSpec.default];
     this.props.onChange(this.props.fieldName, expression);
+
+    this.setState({
+      isExpression: true,
+    });
   }
 
   makeDataFunction = () => {
@@ -152,11 +170,12 @@ export default class FunctionSpecProperty  extends React.Component {
     const propClass = this.props.fieldSpec.default === this.props.value ? "maputnik-default-property" : "maputnik-modified-property"
     let specField;
 
-    if (isExpression(this.props.value, this.props.fieldSpec)) {
+    if (this.state.isExpression) {
       specField = (
         <ExpressionProperty
           error={this.props.error}
           onChange={this.props.onChange.bind(this, this.props.fieldName)}
+          onDelete={this.deleteExpression}
           fieldName={this.props.fieldName}
           fieldSpec={this.props.fieldSpec}
           value={this.props.value}
diff --git a/src/components/fields/_ExpressionProperty.jsx b/src/components/fields/_ExpressionProperty.jsx
index 037a040d..e19eaf66 100644
--- a/src/components/fields/_ExpressionProperty.jsx
+++ b/src/components/fields/_ExpressionProperty.jsx
@@ -8,6 +8,7 @@ import StringInput from '../inputs/StringInput'
 
 import labelFromFieldName from './_labelFromFieldName'
 import stringifyPretty from 'json-stringify-pretty-compact'
+import JSONEditor from '../layers/JSONEditor'
 
 
 function isLiteralExpression (value) {
@@ -16,7 +17,7 @@ function isLiteralExpression (value) {
 
 export default class ExpressionProperty extends React.Component {
   static propTypes = {
-    onDeleteStop: PropTypes.func,
+    onDelete: PropTypes.func,
     fieldName: PropTypes.string,
     fieldSpec: PropTypes.object
   }
@@ -28,21 +29,14 @@ export default class ExpressionProperty extends React.Component {
     };
   }
 
-  onChange = (value) => {
-    try {
-      const jsonVal = JSON.parse(value);
-
-      if (isLiteralExpression(jsonVal)) {
-        this.setState({
-          lastValue: jsonVal
-        });
-      }
-
-      this.props.onChange(jsonVal);
-    }
-    catch (err) {
-      // TODO: Handle JSON parse error
+  onChange = (jsonVal) => {
+    if (isLiteralExpression(jsonVal)) {
+      this.setState({
+        lastValue: jsonVal
+      });
     }
+
+    this.props.onChange(jsonVal);
   }
 
   onDelete = () => {
@@ -50,13 +44,13 @@ export default class ExpressionProperty extends React.Component {
     const {value, fieldName, fieldSpec} = this.props;
 
     if (isLiteralExpression(value)) {
-     this.props.onChange(value[1]);
+     this.props.onDelete(value[1]);
     }
     else if (isLiteralExpression(lastValue)) {
-     this.props.onChange(lastValue[1]);
+     this.props.onDelete(lastValue[1]);
     }
     else {
-      this.props.onChange(fieldSpec.default);
+      this.props.onDelete(fieldSpec.default);
     }
   }
 
@@ -75,12 +69,16 @@ export default class ExpressionProperty extends React.Component {
       doc={this.props.fieldSpec.doc}
       label={labelFromFieldName(this.props.fieldName)}
       action={deleteStopBtn}
+      wideMode={true}
     >
-      <StringInput
-        multi={true}
-        value={stringifyPretty(this.props.value, {indent: 2})}
-        spellCheck={false}
-        onInput={this.onChange}
+      <JSONEditor
+        className="maputnik-expression-editor"
+        layer={this.props.value}
+        lineNumbers={false}
+        maxHeight={200}
+        lineWrapping={true}
+        getValue={(data) => stringifyPretty(data, {indent: 2, maxLength: 50})}
+        onChange={this.onChange}
       />
     </InputBlock>
   }
diff --git a/src/components/inputs/InputBlock.jsx b/src/components/inputs/InputBlock.jsx
index 9cfaacff..f700e463 100644
--- a/src/components/inputs/InputBlock.jsx
+++ b/src/components/inputs/InputBlock.jsx
@@ -28,6 +28,7 @@ class InputBlock extends React.Component {
       data-wd-key={this.props["data-wd-key"]}
       className={classnames({
         "maputnik-input-block": true,
+        "maputnik-input-block--wide": this.props.wideMode,
         "maputnik-action-block": this.props.action
       })}
       >
diff --git a/src/components/layers/JSONEditor.jsx b/src/components/layers/JSONEditor.jsx
index e0a99ec9..eec03431 100644
--- a/src/components/layers/JSONEditor.jsx
+++ b/src/components/layers/JSONEditor.jsx
@@ -1,5 +1,6 @@
 import React from 'react'
 import PropTypes from 'prop-types'
+import classnames from 'classnames';
 
 import InputBlock from '../inputs/InputBlock'
 import StringInput from '../inputs/StringInput'
@@ -22,6 +23,15 @@ class JSONEditor extends React.Component {
     layer: PropTypes.object.isRequired,
     maxHeight: PropTypes.number,
     onChange: PropTypes.func,
+    lineNumbers: PropTypes.bool,
+  }
+
+  static defaultProps = {
+    lineNumbers: true,
+    gutters: ["CodeMirror-lint-markers"],
+    getValue: (data) => {
+      return JSON.stringify(data, null, 2)
+    }
   }
 
   constructor(props) {
@@ -33,7 +43,7 @@ class JSONEditor extends React.Component {
   }
 
   getValue () {
-    return JSON.stringify(this.props.layer, null, 2);
+    return this.props.getValue(this.props.layer);
   }
 
   componentDidMount () {
@@ -43,13 +53,14 @@ class JSONEditor extends React.Component {
         name: "javascript",
         json: true
       },
+      lineWrapping: this.props.lineWrapping,
       tabSize: 2,
       theme: 'maputnik',
       viewportMargin: Infinity,
-      lineNumbers: true,
+      lineNumbers: this.props.lineNumbers,
       lint: true,
       matchBrackets: true,
-      gutters: ["CodeMirror-lint-markers"],
+      gutters: this.props.gutters,
       scrollbarStyle: "null",
     });
 
@@ -113,7 +124,7 @@ class JSONEditor extends React.Component {
     }
 
     return <div
-      className="codemirror-container"
+      className={classnames("codemirror-container", this.props.className)}
       ref={(el) => this._el = el}
       style={style}
     />
diff --git a/src/styles/index.scss b/src/styles/index.scss
index 019857a9..54c11c4b 100644
--- a/src/styles/index.scss
+++ b/src/styles/index.scss
@@ -35,6 +35,7 @@
   height: 14px;
 }
 
+// TODO: Move these into correct *.scss files
 .maputnik-inline-error {
   color: #a4a4a4;
   padding: 0.4em 0.4em;
@@ -43,3 +44,22 @@
   border-radius: 2px;
   margin: $margin-2 0px;
 }
+
+.maputnik-expression-editor {
+  border: solid 1px $color-gray;
+}
+
+.maputnik-input-block--wide {
+  .maputnik-input-block-content {
+    display: block;
+    width: auto;
+  }
+
+  .maputnik-input-block-label {
+    width: 82%;
+  }
+
+  .maputnik-input-block-action {
+    text-align: right;
+  }
+}