diff --git a/include/etl/observer.h b/include/etl/observer.h
index 35e51dee9..32eee70ec 100644
--- a/include/etl/observer.h
+++ b/include/etl/observer.h
@@ -498,6 +498,19 @@ namespace etl
     virtual void notification(T1) = 0;
   };
 
+  //*********************************************************************
+  /// The observer interface for void argument notification type.
+  ///\ingroup observer
+  //*********************************************************************
+  template <>
+  class observer<void>
+  {
+  public:
+
+    virtual ~observer() {}
+    virtual void notification() = 0;
+  };
+
 #endif
 }
 
diff --git a/include/etl/version.h b/include/etl/version.h
index 34db9c980..afdc63a74 100644
--- a/include/etl/version.h
+++ b/include/etl/version.h
@@ -40,7 +40,7 @@ SOFTWARE.
 
 #define ETL_VERSION_MAJOR 20
 #define ETL_VERSION_MINOR 39
-#define ETL_VERSION_PATCH 0
+#define ETL_VERSION_PATCH 1
 
 #define ETL_VERSION       ETL_STRING(ETL_VERSION_MAJOR) "." ETL_STRING(ETL_VERSION_MINOR) "." ETL_STRING(ETL_VERSION_PATCH)
 #define ETL_VERSION_W     ETL_WIDE_STRING(ETL_VERSION_MAJOR) L"." ETL_WIDE_STRING(ETL_VERSION_MINOR) L"." ETL_WIDE_STRING(ETL_VERSION_PATCH)
diff --git a/library.json b/library.json
index bcb615a96..7e17ee746 100644
--- a/library.json
+++ b/library.json
@@ -1,6 +1,6 @@
 {
   "name": "Embedded Template Library",
-  "version": "20.39.0",
+  "version": "20.39.1",
   "authors": {
     "name": "John Wellbelove",
     "email": "john.wellbelove@etlcpp.com"
diff --git a/library.properties b/library.properties
index 719241acf..c18d09f36 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=Embedded Template Library
-version=20.39.0
+version=20.39.1
 author= John Wellbelove <john.wellbelove@etlcpp.com>
 maintainer=John Wellbelove <john.wellbelove@etlcpp.com>
 license=MIT
diff --git a/support/Release notes.txt b/support/Release notes.txt
index 1964ff912..2daac9be0 100644
--- a/support/Release notes.txt	
+++ b/support/Release notes.txt	
@@ -1,4 +1,10 @@
 ===============================================================================
+20.39.1
+
+#940 Allow etl::observer notification without argument
+     Added a void specialisation to the < C++11 code.
+
+===============================================================================
 20.39.0
 
 Refactored:
diff --git a/test/test_observer.cpp b/test/test_observer.cpp
index 48051c808..aff048f07 100644
--- a/test/test_observer.cpp
+++ b/test/test_observer.cpp
@@ -75,6 +75,11 @@ namespace
   // The observer base type that does not take a notification type.
   //*****************************************************************************
   typedef etl::observer<void, int> ObserverVoidIntType;
+#else
+  //*****************************************************************************
+  // The observer base type that does not take a notification type.
+  //*****************************************************************************
+  typedef etl::observer<void> ObserverVoidType;
 #endif
 }
 
@@ -141,6 +146,22 @@ class ObservableVoidInt : public etl::observable<ObserverVoidIntType, 2>
     notify_observers(n);
   }
 };
+#else
+//*****************************************************************************
+// The concrete observable 3 class.
+//*****************************************************************************
+class ObservableVoid : public etl::observable<ObserverVoidType, 2>
+{
+public:
+
+  //*********************************
+  // Notify all of the observers.
+  //*********************************
+  void send_notifications()
+  {
+    notify_observers();
+  }
+};
 #endif
 
 //*****************************************************************************
@@ -260,6 +281,32 @@ class ObserverVoidInt : public ObserverVoidIntType
   // Notification2
   //*******************************************
   void notification(int)  override
+  {
+    ++data2_count;
+  }
+
+  int data1_count;
+  int data2_count;
+};
+#else
+//*****************************************************************************
+// The third observer type.
+// If any one of the overloads is missing or a parameter declaration is incorrect
+// then the class will be 'abstract' and will not compile.
+//*****************************************************************************
+class ObserverVoid : public ObserverVoidType
+{
+public:
+
+  ObserverVoid()
+    : data1_count(0)
+  {
+  }
+
+  //*******************************************
+  // Notification1
+  //*******************************************
+  void notification() override
   {
     ++data1_count;
   }
@@ -572,6 +619,21 @@ namespace
       observable.send_notifications();
       observable.send_notifications(1);
     }
+#else
+    //*************************************************************************
+    TEST(test_void_observable)
+    {
+      // The observable objects.
+      ObservableVoid observable;
+
+      // The observer objects.
+      ObserverVoid observer;
+
+      observable.add_observer(observer);
+
+      // Send the notifications.
+      observable.send_notifications();
+    }
 #endif
   }
 }
diff --git a/version.txt b/version.txt
index 4298195f6..f1d18b950 100644
--- a/version.txt
+++ b/version.txt
@@ -1 +1 @@
-20.39.0
+20.39.1