diff --git a/blocks_vertical/procedures.js b/blocks_vertical/procedures.js
index 1164ce76b7..d5fabec337 100644
--- a/blocks_vertical/procedures.js
+++ b/blocks_vertical/procedures.js
@@ -623,13 +623,15 @@ Blockly.ScratchBlocks.ProcedureUtils.updateDeclarationProcCode_ = function() {
       this.procCode_ += input.fieldRow[0].getValue();
     } else if (input.type == Blockly.INPUT_VALUE) {
       // Inspect the argument editor.
-      var target = input.connection.targetBlock();
-      this.displayNames_.push(target.getFieldValue('TEXT'));
-      this.argumentIds_.push(input.name);
-      if (target.type == 'argument_editor_boolean') {
-        this.procCode_ += '%b';
-      } else {
-        this.procCode_ += '%s';
+      var target = input.connection ? input.connection.targetBlock() : null;
+      if (target) {
+        this.displayNames_.push(target.getFieldValue('TEXT'));
+        this.argumentIds_.push(input.name);
+        if (target.type == 'argument_editor_boolean') {
+          this.procCode_ += '%b';
+        } else {
+          this.procCode_ += '%s';
+        }
       }
     } else {
       throw new Error(
@@ -649,8 +651,10 @@ Blockly.ScratchBlocks.ProcedureUtils.focusLastEditor_ = function() {
       newInput.fieldRow[0].showEditor_();
     } else if (newInput.type == Blockly.INPUT_VALUE) {
       // Inspect the argument editor.
-      var target = newInput.connection.targetBlock();
-      target.getField('TEXT').showEditor_();
+      var target = newInput.connection ? newInput.connection.targetBlock() : null;
+      if (target) {
+        target.getField('TEXT').showEditor_();
+      }
     }
   }
 };
@@ -737,7 +741,7 @@ Blockly.ScratchBlocks.ProcedureUtils.removeFieldCallback = function(field) {
     var input = this.inputList[n];
     if (input.connection) {
       var target = input.connection.targetBlock();
-      if (target.getField(field.name) == field) {
+      if (target && target.getField(field.name) == field) {
         inputNameToRemove = input.name;
       }
     } else {
diff --git a/core/field_customInput.js b/core/field_customInput.js
index acf0a49a7c..638034e3f8 100644
--- a/core/field_customInput.js
+++ b/core/field_customInput.js
@@ -159,6 +159,18 @@ Blockly.FieldCustom.prototype.getValue = function() {
   return this.value_;
 };
 
+/**
+ * Get the text from this field for display and XML serialization.
+ * Return empty string since the actual code is stored in value_ and
+ * should not be serialized as display text.
+ * @return {string} Empty string for display.
+ */
+Blockly.FieldCustom.prototype.getText = function() {
+  // Return empty string to avoid serializing code with special characters
+  // The actual value is handled separately via getValue/setValue
+  return '';
+};
+
 /**
  * do whatever the user desires on-edit
  * @private