diff --git a/src/asciireader.cpp b/src/asciireader.cpp
--- a/src/asciireader.cpp
+++ b/src/asciireader.cpp
@@ -58,6 +58,13 @@ QWidget* AsciiReader::settingsWidget()
     return &_settingsWidget;
 }
 
+unsigned AsciiReader::numChannels() const
+{
+    // TODO: an alternative is to never set _numChannels to '0'
+    // do not allow '0'
+    return _numChannels == 0 ? 1 : _numChannels;
+}
+
 void AsciiReader::enable(bool enabled)
 {
     if (enabled)