diff --git a/blocks/logic.js b/blocks/logic.js
index 5899e04a5..a37387d8f 100644
--- a/blocks/logic.js
+++ b/blocks/logic.js
@@ -564,12 +564,12 @@ Blockly.Constants.Logic.LOGIC_COMPARE_ONCHANGE_MIXIN = {
  * @readonly
  */
 Blockly.Constants.Logic.LOGIC_COMPARE_EXTENSION = function() {
-  // Fix operator labels in RTL
+  // Fix operator labels in RTL.
   if (this.RTL) {
     Blockly.Constants.Logic.fixLogicCompareRtlOpLabels.apply(this);
   }
 
-  // Add onchange handler to ensure types are compatable.
+  // Add onchange handler to ensure types are compatible.
   this.mixin(Blockly.Constants.Logic.LOGIC_COMPARE_ONCHANGE_MIXIN);
 };
 
diff --git a/core/extensions.js b/core/extensions.js
index 774233c8d..5f9a9da29 100644
--- a/core/extensions.js
+++ b/core/extensions.js
@@ -328,7 +328,7 @@ Blockly.Extensions.buildTooltipForDropdown = function(dropdownName,
   // Wait for load, in case Blockly.Msg is not yet populated.
   // runAfterPageLoad() does not run in a Node.js environment due to lack of
   // document object, in which case skip the validation.
-  if (document) {  // Relies on document.readyState
+  if (typeof document == 'object') {  // Relies on document.readyState
     Blockly.utils.runAfterPageLoad(function() {
       for (var key in lookupTable) {
         // Will print warnings if reference is missing.
@@ -409,7 +409,7 @@ Blockly.Extensions.buildTooltipWithFieldValue = function(msgTemplate,
   // Wait for load, in case Blockly.Msg is not yet populated.
   // runAfterPageLoad() does not run in a Node.js environment due to lack of
   // document object, in which case skip the validation.
-  if (document) {  // Relies on document.readyState
+  if (typeof document == 'object') {  // Relies on document.readyState
     Blockly.utils.runAfterPageLoad(function() {
       // Will print warnings if reference is missing.
       Blockly.utils.checkMessageReferences(msgTemplate);
diff --git a/core/utils.js b/core/utils.js
index 8f2179e5c..b715bf470 100644
--- a/core/utils.js
+++ b/core/utils.js
@@ -896,7 +896,7 @@ Blockly.utils.insertAfter_ = function(newNode, refNode) {
  * @throws Error Will throw if no global document can be found (e.g., Node.js).
  */
 Blockly.utils.runAfterPageLoad = function(fn) {
-  if (!document) {
+  if (typeof document != 'object') {
     throw new Error('Blockly.utils.runAfterPageLoad() requires browser document.');
   }
   if (document.readyState === 'complete') {