diff --git a/src/source.cpp b/src/source.cpp
--- a/src/source.cpp
+++ b/src/source.cpp
@@ -26,6 +26,7 @@ void Source::connect(Sink* sink)
     Q_ASSERT(!sinks.contains(sink));
 
     sinks.append(sink);
+    sink->setNumChannels(numChannels(), hasX());
 }
 
 void Source::disconnect(Sink* sink)
@@ -43,10 +44,10 @@ void Source::feedOut(const SamplePack& d
     }
 }
 
-void Source::feedNumChannels(unsigned nc, bool x) const
+void Source::updateNumChannels() const
 {
     for (auto sink : sinks)
     {
-        sink->setNumChannels(nc, x);
+        sink->setNumChannels(numChannels(), hasX());
     }
 }
diff --git a/src/source.h b/src/source.h
--- a/src/source.h
+++ b/src/source.h
@@ -41,8 +41,9 @@ public:
 protected:
     /// Feeds "in" given data to connected sinks
     void feedOut(const SamplePack& data) const;
-    /// Updates "number of channels" of connected sinks
-    void feedNumChannels(unsigned nc, bool x = false) const;
+    /// Updates "number of channels" of connected sinks. Must be
+    /// called when num. channels or hasX changes.
+    void updateNumChannels() const;
 
 private:
     QList<Sink*> sinks;
diff --git a/tests/test.cpp b/tests/test.cpp
--- a/tests/test.cpp
+++ b/tests/test.cpp
@@ -63,7 +63,6 @@ public:
             _hasX = false;
         };
 
-public:
     void feedIn(const SamplePack& data)
         {
             REQUIRE(data.numChannels() == numChannels());
@@ -119,3 +118,65 @@ TEST_CASE("sink", "[memory, stream]")
     REQUIRE(follower.numChannels() == 2);
     REQUIRE(follower.hasX() == true);
 }
+
+class TestSource : public Source
+{
+public:
+    int _numChannels;
+    bool _hasX;
+
+    TestSource(unsigned nc, bool x)
+        {
+            _numChannels = nc;
+            _hasX = x;
+        };
+
+    virtual unsigned numChannels() const
+        {
+            return _numChannels;
+        };
+
+    virtual bool hasX() const
+        {
+            return _hasX;
+        };
+
+    void _feed(const SamplePack& data) const
+        {
+            feedOut(data);
+        };
+
+    void _setNumChannels(unsigned nc, bool x)
+        {
+            _numChannels = nc;
+            _hasX = x;
+
+            updateNumChannels();
+        };
+};
+
+TEST_CASE("source", "[memory, stream]")
+{
+    TestSink sink;
+
+    TestSource source(3, false);
+
+    REQUIRE(source.numChannels() == 3);
+    REQUIRE(source.hasX() == false);
+
+    source.connect(&sink);
+    REQUIRE(sink.numChannels() == 3);
+    REQUIRE(sink.hasX() == false);
+
+    source._setNumChannels(5, true);
+    REQUIRE(sink.numChannels() == 5);
+    REQUIRE(sink.hasX() == true);
+
+    SamplePack pack(100, 5, true);
+    source._feed(pack);
+    REQUIRE(sink.totalFed == 100);
+
+    source.disconnect(&sink);
+    source._feed(pack);
+    REQUIRE(sink.totalFed == 100);
+}