diff --git a/core/interfaces/i_procedure_block.js b/core/interfaces/i_procedure_block.js
index 17502c19a..4e586e040 100644
--- a/core/interfaces/i_procedure_block.js
+++ b/core/interfaces/i_procedure_block.js
@@ -10,19 +10,19 @@
 
 'use strict';
 
-goog.provide('Blockly.Procedures.ProcedureBlock');
+goog.provide('Blockly.IProcedureBlock');
 
 /**
  * A procedure block interface.
  * @interface
  */
-Blockly.Procedures.ProcedureBlock = function() {};
+Blockly.IProcedureBlock = function() {};
 
 /**
  * Returns the name of the procedure the procedure block calls.
  * @return {string}
  */
-Blockly.Procedures.ProcedureBlock.prototype.getProcedureCall;
+Blockly.IProcedureBlock.prototype.getProcedureCall;
 
 /**
  * Renames the procedure from the old name to the new name. If the procedure
@@ -31,7 +31,7 @@ Blockly.Procedures.ProcedureBlock.prototype.getProcedureCall;
  * @param {string} oldName The old name of the procedure.
  * @param {string} newName The new name of hte procedure.
  */
-Blockly.Procedures.ProcedureBlock.prototype.renameProcedure;
+Blockly.IProcedureBlock.prototype.renameProcedure;
 
 /**
  * Returns the signature of the procedure block's procedure definition.
@@ -40,4 +40,4 @@ Blockly.Procedures.ProcedureBlock.prototype.renameProcedure;
  *     - {!Array<string>} a list of all its arguments
  *     - {boolean} whether it has a return value or not
  */
-Blockly.Procedures.ProcedureBlock.prototype.getProcedureDef;
+Blockly.IProcedureBlock.prototype.getProcedureDef;
diff --git a/core/procedures.js b/core/procedures.js
index 03b0210b3..e625b5eb2 100644
--- a/core/procedures.js
+++ b/core/procedures.js
@@ -25,13 +25,13 @@ goog.require('Blockly.Events.BlockChange');
 goog.require('Blockly.Field');
 goog.require('Blockly.Msg');
 goog.require('Blockly.Names');
-goog.require('Blockly.Procedures.ProcedureBlock');
 goog.require('Blockly.utils.xml');
 goog.require('Blockly.Workspace');
 goog.require('Blockly.Xml');
 
 goog.requireType('Blockly.Block');
 goog.requireType('Blockly.Events.Abstract');
+goog.requireType('Blockly.IProcedureBlock');
 goog.requireType('Blockly.WorkspaceSvg');
 
 
@@ -48,6 +48,16 @@ Blockly.Procedures.NAME_TYPE = Blockly.PROCEDURE_CATEGORY_NAME;
  */
 Blockly.Procedures.DEFAULT_ARG = 'x';
 
+/**
+ * A procedure block interface. Will be deprecated for Blockly.IProcedureBlock.
+ * @typedef {{
+ *    getProcedureCall: function():string,
+ *    renameProcedure: function(string,string),
+ *    getProcedureDef: function():!Array
+ * }}
+ */
+Blockly.Procedures.ProcedureBlock;
+
 /**
  * Find all user-created procedure definitions in a workspace.
  * @param {!Blockly.Workspace} root Root workspace.
@@ -59,10 +69,10 @@ Blockly.Procedures.DEFAULT_ARG = 'x';
 Blockly.Procedures.allProcedures = function(root) {
   var proceduresNoReturn = root.getBlocksByType('procedures_defnoreturn', false)
       .map(function(block) {
-        return /** @type {!Blockly.Procedures.ProcedureBlock} */ (block).getProcedureDef();
+        return /** @type {!Blockly.IProcedureBlock} */ (block).getProcedureDef();
       });
   var proceduresReturn = root.getBlocksByType('procedures_defreturn', false).map(function(block) {
-    return /** @type {!Blockly.Procedures.ProcedureBlock} */ (block).getProcedureDef();
+    return /** @type {!Blockly.IProcedureBlock} */ (block).getProcedureDef();
   });
   proceduresNoReturn.sort(Blockly.Procedures.procTupleComparator_);
   proceduresReturn.sort(Blockly.Procedures.procTupleComparator_);
@@ -137,7 +147,7 @@ Blockly.Procedures.isNameUsed = function(name, workspace, opt_exclude) {
       continue;
     }
     if (blocks[i].getProcedureDef) {
-      var procedureBlock = /** @type {!Blockly.Procedures.ProcedureBlock} */ (
+      var procedureBlock = /** @type {!Blockly.IProcedureBlock} */ (
         blocks[i]);
       var procName = procedureBlock.getProcedureDef();
       if (Blockly.Names.equals(procName[0], name)) {
@@ -166,7 +176,7 @@ Blockly.Procedures.rename = function(name) {
     var blocks = this.getSourceBlock().workspace.getAllBlocks(false);
     for (var i = 0; i < blocks.length; i++) {
       if (blocks[i].renameProcedure) {
-        var procedureBlock = /** @type {!Blockly.Procedures.ProcedureBlock} */ (
+        var procedureBlock = /** @type {!Blockly.IProcedureBlock} */ (
           blocks[i]);
         procedureBlock.renameProcedure(
             /** @type {string} */ (oldName), legalName);
@@ -336,7 +346,7 @@ Blockly.Procedures.getCallers = function(name, workspace) {
   // Iterate through every block and check the name.
   for (var i = 0; i < blocks.length; i++) {
     if (blocks[i].getProcedureCall) {
-      var procedureBlock = /** @type {!Blockly.Procedures.ProcedureBlock} */ (
+      var procedureBlock = /** @type {!Blockly.IProcedureBlock} */ (
         blocks[i]);
       var procName = procedureBlock.getProcedureCall();
       // Procedure name may be null if the block is only half-built.
@@ -355,7 +365,7 @@ Blockly.Procedures.getCallers = function(name, workspace) {
  */
 Blockly.Procedures.mutateCallers = function(defBlock) {
   var oldRecordUndo = Blockly.Events.recordUndo;
-  var procedureBlock = /** @type {!Blockly.Procedures.ProcedureBlock} */ (
+  var procedureBlock = /** @type {!Blockly.IProcedureBlock} */ (
     defBlock);
   var name = procedureBlock.getProcedureDef()[0];
   var xmlElement = defBlock.mutationToDom(true);
@@ -391,7 +401,7 @@ Blockly.Procedures.getDefinition = function(name, workspace) {
   var blocks = workspace.getAllBlocks(false);
   for (var i = 0; i < blocks.length; i++) {
     if (blocks[i].getProcedureDef) {
-      var procedureBlock = /** @type {!Blockly.Procedures.ProcedureBlock} */ (
+      var procedureBlock = /** @type {!Blockly.IProcedureBlock} */ (
         blocks[i]);
       var tuple = procedureBlock.getProcedureDef();
       if (tuple && Blockly.Names.equals(tuple[0], name)) {