diff --git a/Foundation/Operation.swift b/Foundation/Operation.swift
index 0a845a0451..8d6e537759 100644
--- a/Foundation/Operation.swift
+++ b/Foundation/Operation.swift
@@ -429,7 +429,7 @@ open class Operation : NSObject {
             }
         }
     }
-    
+
     open func addDependency(_ op: Operation) {
         _addDependency(op)
     }
@@ -668,22 +668,16 @@ open class BlockOperation : Operation {
         }
         _lock()
         defer { _unlock() }
-        if _block == nil && _executionBlocks == nil {
+        if _block == nil {
             _block = block
+        } else if _executionBlocks == nil {
+            _executionBlocks = [block]
         } else {
-            if _executionBlocks == nil {
-                if let existing = _block {
-                    _executionBlocks = [existing, block]
-                } else {
-                    _executionBlocks = [block]
-                }
-            } else {
-                _executionBlocks?.append(block)
-            }
+            _executionBlocks?.append(block)
         }
     }
     
-    open var executionBlocks: [@convention(block) () -> Void] {
+    open var executionBlocks: [() -> Void] {
         get {
             _lock()
             defer { _unlock() }
diff --git a/TestFoundation/TestOperationQueue.swift b/TestFoundation/TestOperationQueue.swift
index 250e521e4a..7a60d7778d 100644
--- a/TestFoundation/TestOperationQueue.swift
+++ b/TestFoundation/TestOperationQueue.swift
@@ -26,6 +26,7 @@ class TestOperationQueue : XCTestCase {
             ("test_CurrentQueueWithUnderlyingQueueResetToNil", test_CurrentQueueWithUnderlyingQueueResetToNil),
             ("test_isSuspended", test_isSuspended),
             ("test_OperationDependencyCount", test_OperationDependencyCount),
+            ("test_BlockOperationAddExecutionBlock", test_BlockOperationAddExecutionBlock)
         ]
     }
     
@@ -279,6 +280,21 @@ class TestOperationQueue : XCTestCase {
         op1.addDependency(op2)
         XCTAssert(op1.dependencies.count == 1)
     }
+    
+    func test_BlockOperationAddExecutionBlock() {
+        var msgOperations = [String]()
+        let blockOperation = BlockOperation {
+            msgOperations.append("block1 executed")
+        }
+        blockOperation.addExecutionBlock {
+            msgOperations.append("block2 executec")
+        }
+        XCTAssert(blockOperation.executionBlocks.count == 2)
+        let queue = OperationQueue()
+        queue.addOperation(blockOperation)
+        queue.waitUntilAllOperationsAreFinished()
+        XCTAssertEqual(msgOperations, ["block1 executed", "block2 executec"])
+    }
 }
 
 class AsyncOperation: Operation {