diff --git a/src/blocks/scratch3_procedures.js b/src/blocks/scratch3_procedures.js
index b91630f12..22e2f788f 100644
--- a/src/blocks/scratch3_procedures.js
+++ b/src/blocks/scratch3_procedures.js
@@ -13,17 +13,18 @@ class Scratch3ProcedureBlocks {
      */
     getPrimitives () {
         return {
-            procedures_defnoreturn: this.defNoReturn,
-            procedures_callnoreturn: this.callNoReturn,
-            procedures_param: this.param
+            procedures_definition: this.definition,
+            procedures_call: this.call,
+            argument_reporter_string_number: this.param,
+            argument_reporter_boolean: this.param
         };
     }
 
-    defNoReturn () {
+    definition () {
         // No-op: execute the blocks.
     }
 
-    callNoReturn (args, util) {
+    call (args, util) {
         if (!util.stackFrame.executed) {
             const procedureCode = args.mutation.proccode;
             const paramNames = util.getProcedureParamNames(procedureCode);
@@ -47,7 +48,7 @@ class Scratch3ProcedureBlocks {
     }
 
     param (args, util) {
-        const value = util.getParam(args.mutation.paramname);
+        const value = util.getParam(args.VALUE);
         return value;
     }
 }
diff --git a/src/engine/blocks.js b/src/engine/blocks.js
index 92a2d58e7..1aa97d28d 100644
--- a/src/engine/blocks.js
+++ b/src/engine/blocks.js
@@ -152,8 +152,7 @@ class Blocks {
         for (const id in this._blocks) {
             if (!this._blocks.hasOwnProperty(id)) continue;
             const block = this._blocks[id];
-            if (block.opcode === 'procedures_defnoreturn' ||
-                block.opcode === 'procedures_defreturn') {
+            if (block.opcode === 'procedures_definition') {
                 const internal = this._getCustomBlockInternal(block);
                 if (internal && internal.mutation.proccode === name) {
                     return id; // The outer define block id
@@ -172,7 +171,7 @@ class Blocks {
         for (const id in this._blocks) {
             if (!this._blocks.hasOwnProperty(id)) continue;
             const block = this._blocks[id];
-            if (block.opcode === 'procedures_callnoreturn_internal' &&
+            if (block.opcode === 'procedures_prototype' &&
                 block.mutation.proccode === name) {
                 return JSON.parse(block.mutation.argumentnames);
             }
diff --git a/src/engine/thread.js b/src/engine/thread.js
index 3b8ce32bd..def1fc1ef 100644
--- a/src/engine/thread.js
+++ b/src/engine/thread.js
@@ -164,7 +164,7 @@ class Thread {
         let blockID = this.peekStack();
         while (blockID !== null) {
             const block = this.target.blocks.getBlock(blockID);
-            if (typeof block !== 'undefined' && block.opcode === 'procedures_callnoreturn') {
+            if (typeof block !== 'undefined' && block.opcode === 'procedures_call') {
                 break;
             }
             this.popStack();
@@ -271,7 +271,7 @@ class Thread {
         const sp = this.stack.length - 1;
         for (let i = sp - 1; i >= 0; i--) {
             const block = this.target.blocks.getBlock(this.stack[i]);
-            if (block.opcode === 'procedures_callnoreturn' &&
+            if (block.opcode === 'procedures_call' &&
                 block.mutation.proccode === procedureCode) {
                 return true;
             }
diff --git a/src/serialization/sb2.js b/src/serialization/sb2.js
index 2a54d40a7..16b63da88 100644
--- a/src/serialization/sb2.js
+++ b/src/serialization/sb2.js
@@ -518,7 +518,7 @@ const parseBlock = function (sb2block, getVariableId, extensions) {
         };
         activeBlock.children = [{
             id: inputUid,
-            opcode: 'procedures_callnoreturn_internal',
+            opcode: 'procedures_prototype',
             inputs: {},
             fields: {},
             next: null,
@@ -544,13 +544,15 @@ const parseBlock = function (sb2block, getVariableId, extensions) {
             argumentids: JSON.stringify(parseProcedureArgIds(sb2block[1]))
         };
     } else if (oldOpcode === 'getParam') {
-        // Mutation for procedure parameter.
-        activeBlock.mutation = {
-            tagName: 'mutation',
-            children: [],
-            paramname: sb2block[1], // Name of parameter.
-            shape: sb2block[2] // Shape - in 2.0, 'r' or 'b'.
-        };
+        // Assign correct opcode based on the block shape.
+        switch (sb2block[2]) {
+        case 'r':
+            activeBlock.opcode = 'argument_reporter_string_number';
+            break;
+        case 'b':
+            activeBlock.opcode = 'argument_reporter_boolean';
+            break;
+        }
     }
     return activeBlock;
 };
diff --git a/src/serialization/sb2_specmap.js b/src/serialization/sb2_specmap.js
index b511d59c8..70bb0345c 100644
--- a/src/serialization/sb2_specmap.js
+++ b/src/serialization/sb2_specmap.js
@@ -1382,15 +1382,21 @@ const specMap = {
         ]
     },
     'procDef': {
-        opcode: 'procedures_defnoreturn',
+        opcode: 'procedures_definition',
         argMap: []
     },
     'getParam': {
-        opcode: 'procedures_param',
-        argMap: []
+        // Doesn't map to single opcode. Import step assigns final correct opcode.
+        opcode: 'argument_reporter_string_number',
+        argMap: [
+            {
+                type: 'field',
+                fieldName: 'VALUE'
+            }
+        ]
     },
     'call': {
-        opcode: 'procedures_callnoreturn',
+        opcode: 'procedures_call',
         argMap: []
     }
 };
diff --git a/test/unit/engine_sequencer.js b/test/unit/engine_sequencer.js
index abf7102d2..751e9bb64 100644
--- a/test/unit/engine_sequencer.js
+++ b/test/unit/engine_sequencer.js
@@ -36,7 +36,7 @@ const generateBlock = function (id) {
         block: 'fakeBlock',
         name: 'fakeName',
         next: null,
-        opcode: 'procedures_defnoreturn',
+        opcode: 'procedures_definition',
         mutation: {proccode: 'fakeCode'},
         parent: null,
         shadow: false,
@@ -55,7 +55,7 @@ const generateBlockInput = function (id, next, inp) {
         block: 'fakeBlock',
         name: 'fakeName',
         next: next,
-        opcode: 'procedures_defnoreturn',
+        opcode: 'procedures_definition',
         mutation: {proccode: 'fakeCode'},
         parent: null,
         shadow: false,
@@ -156,7 +156,7 @@ test('stepToProcedure', t => {
 
     th.target.blocks.createBlock({
         id: 'internalId',
-        opcode: 'procedures_callnoreturn_internal',
+        opcode: 'procedures_prototype',
         mutation: {
             proccode: 'othercode'
         }
diff --git a/test/unit/engine_thread.js b/test/unit/engine_thread.js
index 60419d360..6c9a9e4f2 100644
--- a/test/unit/engine_thread.js
+++ b/test/unit/engine_thread.js
@@ -194,7 +194,7 @@ test('stopThisScript', t => {
         block: 'fakeBlock',
         name: 'STEPS',
         next: null,
-        opcode: 'procedures_callnoreturn',
+        opcode: 'procedures_call',
         mutation: {proccode: 'fakeCode'},
         parent: null,
         shadow: false,
@@ -246,7 +246,7 @@ test('isRecursiveCall', t => {
         block: 'fakeBlock',
         name: 'STEPS',
         next: null,
-        opcode: 'procedures_callnoreturn',
+        opcode: 'procedures_call',
         mutation: {proccode: 'fakeCode'},
         parent: null,
         shadow: false,