diff --git a/ReactiveKit.podspec b/ReactiveKit.podspec
index 888c4d3..ebe2728 100644
--- a/ReactiveKit.podspec
+++ b/ReactiveKit.podspec
@@ -1,12 +1,12 @@
 Pod::Spec.new do |s|
   s.name             = "ReactiveKit"
-  s.version          = "2.0.2"
+  s.version          = "2.0.3"
   s.summary          = "A Swift Reactive Programming Framework"
   s.description      = "ReactiveKit is a collection of Swift frameworks for reactive and functional reactive programming."
   s.homepage         = "https://github.com/ReactiveKit/ReactiveKit"
   s.license          = 'MIT'
   s.author           = { "Srdan Rasic" => "srdan.rasic@gmail.com" }
-  s.source           = { :git => "https://github.com/ReactiveKit/ReactiveKit.git", :tag => "v2.0.2" }
+  s.source           = { :git => "https://github.com/ReactiveKit/ReactiveKit.git", :tag => "v2.0.3" }
 
   s.ios.deployment_target       = '8.0'
   s.osx.deployment_target       = '10.9'
diff --git a/ReactiveKit/Info.plist b/ReactiveKit/Info.plist
index a16c895..0de69c1 100644
--- a/ReactiveKit/Info.plist
+++ b/ReactiveKit/Info.plist
@@ -15,7 +15,7 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>2.0.2</string>
+	<string>2.0.3</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>
diff --git a/Sources/Operation.swift b/Sources/Operation.swift
index a9fdece..6e652e4 100644
--- a/Sources/Operation.swift
+++ b/Sources/Operation.swift
@@ -810,8 +810,7 @@ extension OperationType {
                         failure: (Error -> ())? = nil,
                         start: (() -> Void)? = nil,
                         completed: (() -> Void)? = nil,
-                        disposed: (() -> ())? = nil,
-                        terminated: (() -> ())? = nil
+                        disposed: (() -> ())? = nil
     ) -> Operation<Element, Error> {
     return Operation { observer in
       start?()
@@ -821,17 +820,14 @@ extension OperationType {
           next?(value)
         case .Failure(let error):
           failure?(error)
-          terminated?()
         case .Completed:
           completed?()
-          terminated?()
         }
         observer.observer(event)
       }
       return BlockDisposable {
         disposable.dispose()
         disposed?()
-        terminated?()
       }
     }
   }
@@ -895,7 +891,7 @@ extension OperationType {
   /// Updates the given subject with `true` when the receiver starts and with `false` when the receiver terminates.
   @warn_unused_result
   public func feedActivityInto<S: SubjectType where S.Event.Element == Bool>(listener: S) -> Operation<Element, Error> {
-    return doOn(start: { listener.next(true) }, terminated: { listener.next(false) })
+    return doOn(start: { listener.next(true) }, disposed: { listener.next(false) })
   }
 
   /// Updates the given subject with .Next element.
diff --git a/Sources/RawStream.swift b/Sources/RawStream.swift
index 35998aa..d80489c 100644
--- a/Sources/RawStream.swift
+++ b/Sources/RawStream.swift
@@ -49,6 +49,29 @@ extension _StreamType {
       }
     }
   }
+
+  /// Register an observer that will be executed on `.Completed` event.
+  @warn_unused_result
+  public func observeCompleted(observer: () -> Void) -> Disposable {
+    return observe { event in
+      if event.isCompletion {
+        observer()
+      }
+    }
+  }
+}
+
+extension _StreamType where Event: Errorable {
+
+  /// Register an observer that will receive error from `.Error` event of the stream.
+  @warn_unused_result
+  public func observeError(observer: Event.Error -> Void) -> Disposable {
+    return observe { event in
+      if let error = event.error {
+        observer(error)
+      }
+    }
+  }
 }
 
 // MARK: - RawStreamType
@@ -74,17 +97,23 @@ public struct RawStream<Event: EventType>: RawStreamType {
   /// Register an observer that will receive events from a stream.
   @warn_unused_result
   public func observe(observer: Event -> Void) -> Disposable {
+    let serialDisposable = SerialDisposable(otherDisposable: nil)
+    let lock = RecursiveLock(name: "observe")
     var terminated = false
     let observer = Observer<Event> { event in
-      guard !terminated else { return }
-      terminated = event.isTermination
-      observer(event)
-    }
-    let disposable = producer(observer)
-    return BlockDisposable {
-      terminated = true
-      disposable.dispose()
+      lock.atomic {
+        guard !serialDisposable.isDisposed && !terminated else { return }
+        if event.isTermination {
+          terminated = true
+          observer(event)
+          serialDisposable.dispose()
+        } else {
+          observer(event)
+        }
+      }
     }
+    serialDisposable.otherDisposable = producer(observer)
+    return serialDisposable
   }
 }
 
diff --git a/Sources/Stream.swift b/Sources/Stream.swift
index ff43554..ccf18b3 100644
--- a/Sources/Stream.swift
+++ b/Sources/Stream.swift
@@ -606,8 +606,7 @@ extension StreamType {
   public func doOn(next next: (Element -> ())? = nil,
                         start: (() -> Void)? = nil,
                         completed: (() -> Void)? = nil,
-                        disposed: (() -> ())? = nil,
-                        terminated: (() -> ())? = nil) -> Stream<Element> {
+                        disposed: (() -> ())? = nil) -> Stream<Element> {
     return Stream { observer in
       start?()
       let disposable = self.observe { event in
@@ -616,14 +615,12 @@ extension StreamType {
           next?(value)
         case .Completed:
           completed?()
-          terminated?()
         }
         observer.observer(event)
       }
       return BlockDisposable {
         disposable.dispose()
         disposed?()
-        terminated?()
       }
     }
   }
@@ -662,7 +659,7 @@ extension StreamType {
   /// Updates the given subject with `true` when the receiver starts and with `false` when the receiver terminates.
   @warn_unused_result
   public func feedActivityInto<S: SubjectType where S.Event.Element == Bool>(listener: S) -> Stream<Element> {
-    return doOn(start: { listener.next(true) }, terminated: { listener.next(false) })
+    return doOn(start: { listener.next(true) }, disposed: { listener.next(false) })
   }
 
   /// Updates the given subject with .Next elements.
diff --git a/Tests/OperationTests.swift b/Tests/OperationTests.swift
index 621f9fe..d51920f 100644
--- a/Tests/OperationTests.swift
+++ b/Tests/OperationTests.swift
@@ -294,15 +294,13 @@ class OperatorsTests: XCTestCase {
     var next = 0
     var completed = 0
     var disposed = 0
-    var terminated = 0
 
-    let d = operation.doOn(next: { _ in next += 1 }, start: { start += 1}, completed: { completed += 1}, disposed: { disposed += 1}, terminated: { terminated += 1 }).observe { _ in }
+    let d = operation.doOn(next: { _ in next += 1 }, start: { start += 1}, completed: { completed += 1}, disposed: { disposed += 1}).observe { _ in }
 
     XCTAssert(start == 1)
     XCTAssert(next == 3)
     XCTAssert(completed == 1)
-    XCTAssert(disposed == 0)
-    XCTAssert(terminated == 1)
+    XCTAssert(disposed == 1)
 
     d.dispose()
     XCTAssert(disposed == 1)
diff --git a/Tests/StreamTests.swift b/Tests/StreamTests.swift
index c858036..b53a23b 100644
--- a/Tests/StreamTests.swift
+++ b/Tests/StreamTests.swift
@@ -250,15 +250,13 @@ class StreamTests: XCTestCase {
     var next = 0
     var completed = 0
     var disposed = 0
-    var terminated = 0
 
-    let d = stream.doOn(next: { _ in next += 1 }, start: { start += 1}, completed: { completed += 1}, disposed: { disposed += 1}, terminated: { terminated += 1 }).observe { _ in }
+    let d = stream.doOn(next: { _ in next += 1 }, start: { start += 1}, completed: { completed += 1}, disposed: { disposed += 1}).observe { _ in }
 
     XCTAssert(start == 1)
     XCTAssert(next == 3)
     XCTAssert(completed == 1)
-    XCTAssert(disposed == 0)
-    XCTAssert(terminated == 1)
+    XCTAssert(disposed == 1)
 
     d.dispose()
     XCTAssert(disposed == 1)