diff --git a/core/block_svg.js b/core/block_svg.js
index e8626e9ae..4d9032e5f 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -262,6 +262,7 @@ Blockly.BlockSvg.prototype.getIcons = function() {
 /**
  * Set parent of this block to be a new block or null.
  * @param {Blockly.BlockSvg} newParent New parent block.
+ * @override
  */
 Blockly.BlockSvg.prototype.setParent = function(newParent) {
   var oldParent = this.parentBlock_;
@@ -894,10 +895,10 @@ Blockly.BlockSvg.prototype.getSvgRoot = function() {
 
 /**
  * Dispose of this block.
- * @param {boolean} healStack If true, then try to heal any gap by connecting
+ * @param {boolean=} healStack If true, then try to heal any gap by connecting
  *     the next statement with the previous statement.  Otherwise, dispose of
  *     all children of this block.
- * @param {boolean} animate If true, show a disposal animation and sound.
+ * @param {boolean=} animate If true, show a disposal animation and sound.
  */
 Blockly.BlockSvg.prototype.dispose = function(healStack, animate) {
   if (!this.workspace) {
diff --git a/core/dropdowndiv.js b/core/dropdowndiv.js
index 62e310794..426bdab04 100644
--- a/core/dropdowndiv.js
+++ b/core/dropdowndiv.js
@@ -199,7 +199,7 @@ Blockly.DropDownDiv.setCategory = function(category) {
  * @param {!Blockly.Block} block Block to position the drop-down around.
  * @param {Function=} opt_onHide Optional callback for when the drop-down is
  *   hidden.
- * @param {number} opt_secondaryYOffset Optional Y offset for above-block
+ * @param {number=} opt_secondaryYOffset Optional Y offset for above-block
  *   positioning.
  * @return {boolean} True if the menu rendered below block; false if above.
  */
diff --git a/core/field.js b/core/field.js
index 7d45ca4a4..ffc903d82 100644
--- a/core/field.js
+++ b/core/field.js
@@ -887,7 +887,7 @@ Blockly.Field.prototype.onMouseDown_ = function(e) {
 
 /**
  * Change the tooltip text for this field.
- * @param {string|function|!Element} newTip Text for tooltip or a parent
+ * @param {string|Function|!Element} newTip Text for tooltip or a parent
  *    element to link to for its tooltip.
  */
 Blockly.Field.prototype.setTooltip = function(newTip) {
diff --git a/core/field_angle.js b/core/field_angle.js
index 75e65fb62..842eaf081 100644
--- a/core/field_angle.js
+++ b/core/field_angle.js
@@ -337,6 +337,7 @@ Blockly.FieldAngle.prototype.updateGraph_ = function() {
  * @param {string|number=} newValue The input value.
  * @return {?number} A valid angle, or null if invalid.
  * @protected
+ * @override
  */
 Blockly.FieldAngle.prototype.doClassValidation_ = function(newValue) {
   if (isNaN(newValue)) {
diff --git a/core/field_image.js b/core/field_image.js
index 23737e15f..fc8a21fa8 100644
--- a/core/field_image.js
+++ b/core/field_image.js
@@ -36,7 +36,7 @@ goog.require('goog.math.Size');
 
 /**
  * Class for an image on a block.
- * @param {string=} src The URL of the image. Defaults to an empty string.
+ * @param {string} src The URL of the image. Defaults to an empty string.
  * @param {!(string|number)} width Width of the image.
  * @param {!(string|number)} height Height of the image.
  * @param {string=} opt_alt Optional alt text for when block is collapsed.
@@ -50,6 +50,9 @@ Blockly.FieldImage = function(src, width, height,
     opt_alt, opt_onClick, opt_flipRtl) {
   this.sourceBlock_ = null;
 
+  if (!src) {
+    throw Error('Src value of an image field is required');
+  }
 
   if (isNaN(height) || isNaN(width)) {
     throw Error('Height and width values of an image field must cast to' +
diff --git a/core/field_number.js b/core/field_number.js
index 2e729d193..807158077 100644
--- a/core/field_number.js
+++ b/core/field_number.js
@@ -39,6 +39,7 @@ goog.require('Blockly.FieldTextInput');
  * @param {Function=} opt_validator A function that is called to validate
  *    changes to the field's value. Takes in a number & returns a validated
  *    number, or null to abort the change.
+ * @extends {Blockly.FieldTextInput}
  * @constructor
  */
 Blockly.FieldNumber = function(opt_value, opt_min, opt_max, opt_precision,
@@ -105,6 +106,7 @@ Blockly.FieldNumber.prototype.setConstraints = function(min, max, precision) {
  * @param {string|number=} newValue The input value.
  * @return {?number} A valid number, or null if invalid.
  * @protected
+ * @override
  */
 Blockly.FieldNumber.prototype.doClassValidation_ = function(newValue) {
   if (newValue === null || newValue === undefined) {
diff --git a/core/rendered_connection.js b/core/rendered_connection.js
index 1a4ae30fa..586dfaac6 100644
--- a/core/rendered_connection.js
+++ b/core/rendered_connection.js
@@ -320,7 +320,7 @@ Blockly.RenderedConnection.prototype.hideAll = function() {
 /**
  * Check if the two connections can be dragged to connect to each other.
  * @param {!Blockly.Connection} candidate A nearby connection to check.
- * @param {number} maxRadius The maximum radius allowed for connections, in
+ * @param {number=} maxRadius The maximum radius allowed for connections, in
  *     workspace units.
  * @return {boolean} True if the connection is allowed, false otherwise.
  */
diff --git a/core/theme.js b/core/theme.js
index cda37fd5b..acca71a4a 100644
--- a/core/theme.js
+++ b/core/theme.js
@@ -27,16 +27,29 @@ goog.provide('Blockly.Theme');
 
 
 /**
- * A block style or a category style.
- * @typedef {!Object.<string, string>}
- */
-Blockly.Theme.Style;
+ * A block style.
+ * @typedef {{
+  *            colourPrimary:string,
+  *            colourSecondary:string,
+  *            colourTertiary:string,
+  *            hat:string
+  *          }}
+  */
+Blockly.Theme.BlockStyle;
+
+/**
+ * A category style.
+ * @typedef {{
+  *            colour:string
+  *          }}
+  */
+Blockly.Theme.CategoryStyle;
 
 /**
  * Class for a theme.
- * @param {!Object.<string, Blockly.Theme.Style>} blockStyles A map from style
+ * @param {!Object.<string, Blockly.Theme.BlockStyle>} blockStyles A map from style
  *     names (strings) to objects with style attributes relating to blocks.
- * @param {!Object.<string, Blockly.Theme.Style>} categoryStyles A map from
+ * @param {!Object.<string, Blockly.Theme.CategoryStyle>} categoryStyles A map from
  *     style names (strings) to objects with style attributes relating to
  *     categories.
  * @constructor
@@ -48,7 +61,7 @@ Blockly.Theme = function(blockStyles, categoryStyles) {
 
 /**
  * Overrides or adds all values from blockStyles to blockStyles_
- * @param {Object.<string, Blockly.Theme.Style>} blockStyles Map of
+ * @param {Object.<string, Blockly.Theme.BlockStyle>} blockStyles Map of
  *     block styles.
  */
 Blockly.Theme.prototype.setAllBlockStyles = function(blockStyles) {
@@ -59,7 +72,7 @@ Blockly.Theme.prototype.setAllBlockStyles = function(blockStyles) {
 
 /**
  * Gets a map of all the block style names.
- * @return {!Object.<string, Blockly.Theme.Style>} Map of block styles.
+ * @return {!Object.<string, Blockly.Theme.BlockStyle>} Map of block styles.
  */
 Blockly.Theme.prototype.getAllBlockStyles = function() {
   return this.blockStyles_;
@@ -68,7 +81,7 @@ Blockly.Theme.prototype.getAllBlockStyles = function() {
 /**
  * Gets the BlockStyle for the given block style name.
  * @param {string} blockStyleName The name of the block style.
- * @return {Blockly.Theme.Style|undefined} The named block style.
+ * @return {Blockly.Theme.BlockStyle|undefined} The named block style.
  */
 Blockly.Theme.prototype.getBlockStyle = function(blockStyleName) {
   return this.blockStyles_[blockStyleName];
@@ -77,7 +90,7 @@ Blockly.Theme.prototype.getBlockStyle = function(blockStyleName) {
 /**
  * Overrides or adds a style to the blockStyles map.
  * @param {string} blockStyleName The name of the block style.
- * @param {Blockly.Theme.Style} blockStyle The block style.
+ * @param {Blockly.Theme.BlockStyle} blockStyle The block style.
 */
 Blockly.Theme.prototype.setBlockStyle = function(blockStyleName, blockStyle) {
   this.blockStyles_[blockStyleName] = blockStyle;
@@ -86,7 +99,7 @@ Blockly.Theme.prototype.setBlockStyle = function(blockStyleName, blockStyle) {
 /**
  * Gets the CategoryStyle for the given category style name.
  * @param {string} categoryStyleName The name of the category style.
- * @return {Blockly.Theme.Style|undefined} The named category style.
+ * @return {Blockly.Theme.CategoryStyle|undefined} The named category style.
  */
 Blockly.Theme.prototype.getCategoryStyle = function(categoryStyleName) {
   return this.categoryStyles_[categoryStyleName];
@@ -95,7 +108,7 @@ Blockly.Theme.prototype.getCategoryStyle = function(categoryStyleName) {
 /**
  * Overrides or adds a style to the categoryStyles map.
  * @param {string} categoryStyleName The name of the category style.
- * @param {Blockly.Theme.Style} categoryStyle The category style.
+ * @param {Blockly.Theme.CategoryStyle} categoryStyle The category style.
 */
 Blockly.Theme.prototype.setCategoryStyle = function(categoryStyleName,
     categoryStyle) {
diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index 2b3f3ef52..e3653b5fc 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -671,6 +671,7 @@ Blockly.WorkspaceSvg.prototype.dispose = function() {
  * @param {string=} opt_id Optional ID.  Use this ID if provided, otherwise
  *     create a new ID.
  * @return {!Blockly.BlockSvg} The created block.
+ * @override
  */
 Blockly.WorkspaceSvg.prototype.newBlock = function(prototypeName, opt_id) {
   return new Blockly.BlockSvg(this, prototypeName, opt_id);
diff --git a/tests/mocha/field_image_test.js b/tests/mocha/field_image_test.js
index ca39f0c22..c175d3dda 100644
--- a/tests/mocha/field_image_test.js
+++ b/tests/mocha/field_image_test.js
@@ -25,9 +25,6 @@ suite ('Image Fields', function() {
     assertEquals(actualValue, expectedValue);
     assertEquals(actualText, expectedText);
   }
-  function assertValueDefault(imageField) {
-    assertValue(imageField, '', '');
-  }
   suite('Constructor', function() {
     test('Empty', function() {
       chai.assert.throws(function() {
@@ -35,12 +32,14 @@ suite ('Image Fields', function() {
       });
     });
     test('Null Src', function() {
-      var imageField = new Blockly.FieldImage(null, 1, 1);
-      assertValueDefault(imageField);
+      chai.assert.throws(function() {
+        new Blockly.FieldImage(null, 1, 1);
+      });
     });
     test('Undefined Src', function() {
-      var imageField = new Blockly.FieldImage(undefined, 1, 1);
-      assertValueDefault(imageField);
+      chai.assert.throws(function() {
+        new Blockly.FieldImage(undefined, 1, 1);
+      });
     });
     test('Null Size', function() {
       chai.assert.throws(function() {
@@ -81,20 +80,22 @@ suite ('Image Fields', function() {
       });
     });
     test('Null Src', function() {
-      var imageField = Blockly.FieldImage.fromJson({
-        src: null,
-        width: 1,
-        height: 1
+      chai.assert.throws(function() {
+        Blockly.FieldImage.fromJson({
+          src: null,
+          width: 1,
+          height: 1
+        });
       });
-      assertValueDefault(imageField);
     });
     test('Undefined Src', function() {
-      var imageField = Blockly.FieldImage.fromJson({
-        src: undefined,
-        width: 1,
-        height: 1
+      chai.assert.throws(function() {
+        Blockly.FieldImage.fromJson({
+          src: undefined,
+          width: 1,
+          height: 1
+        });
       });
-      assertValueDefault(imageField);
     });
     test('Null Size', function() {
       chai.assert.throws(function() {