diff --git a/src/blocks/scratch3_procedures.js b/src/blocks/scratch3_procedures.js
index 7fb31d28f..5caea72ee 100644
--- a/src/blocks/scratch3_procedures.js
+++ b/src/blocks/scratch3_procedures.js
@@ -27,20 +27,22 @@ class Scratch3ProcedureBlocks {
     call (args, util) {
         if (!util.stackFrame.executed) {
             const procedureCode = args.mutation.proccode;
-            const paramNamesAndIds = util.getProcedureParamNamesAndIds(procedureCode);
+            const paramNamesIdsAndDefaults = util.getProcedureParamNamesIdsAndDefaults(procedureCode);
 
             // If null, procedure could not be found, which can happen if custom
             // block is dragged between sprites without the definition.
             // Match Scratch 2.0 behavior and noop.
-            if (paramNamesAndIds === null) {
+            if (paramNamesIdsAndDefaults === null) {
                 return;
             }
 
-            const [paramNames, paramIds] = paramNamesAndIds;
+            const [paramNames, paramIds, paramDefaults] = paramNamesIdsAndDefaults;
 
             for (let i = 0; i < paramIds.length; i++) {
                 if (args.hasOwnProperty(paramIds[i])) {
                     util.pushParam(paramNames[i], args[paramIds[i]]);
+                } else {
+                    util.pushParam(paramNames[i], paramDefaults[i]);
                 }
             }
 
diff --git a/src/engine/block-utility.js b/src/engine/block-utility.js
index b456d02fa..c55ba3bf3 100644
--- a/src/engine/block-utility.js
+++ b/src/engine/block-utility.js
@@ -104,7 +104,7 @@ class BlockUtility {
     }
 
     /**
-     * Get names for parameters for the given procedure.
+     * Get names and ids of parameters for the given procedure.
      * @param {string} procedureCode Procedure code for procedure to query.
      * @return {Array.<string>} List of param names for a procedure.
      */
@@ -112,6 +112,15 @@ class BlockUtility {
         return this.thread.target.blocks.getProcedureParamNamesAndIds(procedureCode);
     }
 
+    /**
+     * Get names, ids, and defaults of parameters for the given procedure.
+     * @param {string} procedureCode Procedure code for procedure to query.
+     * @return {Array.<string>} List of param names for a procedure.
+     */
+    getProcedureParamNamesIdsAndDefaults (procedureCode) {
+        return this.thread.target.blocks.getProcedureParamNamesIdsAndDefaults(procedureCode);
+    }
+
     /**
      * Store a procedure parameter value by its name.
      * @param {string} paramName The procedure's parameter name.
diff --git a/src/engine/blocks.js b/src/engine/blocks.js
index 61493f040..28ac3184f 100644
--- a/src/engine/blocks.js
+++ b/src/engine/blocks.js
@@ -230,11 +230,20 @@ class Blocks {
     }
 
     /**
-     * Get names of parameters for the given procedure.
+     * Get names and ids of parameters for the given procedure.
      * @param {?string} name Name of procedure to query.
      * @return {?Array.<string>} List of param names for a procedure.
      */
     getProcedureParamNamesAndIds (name) {
+        return this.getProcedureParamNamesIdsAndDefaults(name).slice(0, 2);
+    }
+
+    /**
+     * Get names, ids, and defaults of parameters for the given procedure.
+     * @param {?string} name Name of procedure to query.
+     * @return {?Array.<string>} List of param names for a procedure.
+     */
+    getProcedureParamNamesIdsAndDefaults (name) {
         const cachedNames = this._cache.procedureParamNames[name];
         if (typeof cachedNames !== 'undefined') {
             return cachedNames;
@@ -247,7 +256,9 @@ class Blocks {
                 block.mutation.proccode === name) {
                 const names = JSON.parse(block.mutation.argumentnames);
                 const ids = JSON.parse(block.mutation.argumentids);
-                this._cache.procedureParamNames[name] = [names, ids];
+                const defaults = JSON.parse(block.mutation.argumentdefaults);
+
+                this._cache.procedureParamNames[name] = [names, ids, defaults];
                 return this._cache.procedureParamNames[name];
             }
         }
diff --git a/test/fixtures/execute/procedures-recursive-default-boolean.sb2 b/test/fixtures/execute/procedures-recursive-default-boolean.sb2
new file mode 100644
index 000000000..b2873d2e1
Binary files /dev/null and b/test/fixtures/execute/procedures-recursive-default-boolean.sb2 differ
diff --git a/test/fixtures/execute/procedures-recursive-default-number.sb2 b/test/fixtures/execute/procedures-recursive-default-number.sb2
new file mode 100644
index 000000000..cb7263488
Binary files /dev/null and b/test/fixtures/execute/procedures-recursive-default-number.sb2 differ
diff --git a/test/fixtures/execute/procedures-recursive-default-string.sb2 b/test/fixtures/execute/procedures-recursive-default-string.sb2
new file mode 100644
index 000000000..bc1b4a99f
Binary files /dev/null and b/test/fixtures/execute/procedures-recursive-default-string.sb2 differ
diff --git a/test/unit/blocks_procedures.js b/test/unit/blocks_procedures.js
index 0285b23d0..b87674bb7 100644
--- a/test/unit/blocks_procedures.js
+++ b/test/unit/blocks_procedures.js
@@ -16,7 +16,7 @@ test('calling a custom block with no definition does not throw', t => {
         }
     };
     const util = {
-        getProcedureParamNamesAndIds: () => null,
+        getProcedureParamNamesIdsAndDefaults: () => null,
         stackFrame: {
             executed: false
         }