diff --git a/libs/ardour/session_time.cc b/libs/ardour/session_time.cc
index 82063e4dc2..d3cc042bd1 100644
--- a/libs/ardour/session_time.cc
+++ b/libs/ardour/session_time.cc
@@ -258,6 +258,11 @@ Session::convert_to_samples (AnyTime const & position)
 	case AnyTime::Samples:
 		return position.samples;
 		break;
+
+	case AnyTime::BBT_Offset:
+		fatal << X_("programming error: Session::convert_to_samples() called with BBT_Offset\n") << endmsg;
+		/*NOTREACHED*/
+		break;
 	}
 
 	return position.samples;
@@ -293,6 +298,11 @@ Session::any_duration_to_samples (samplepos_t position, AnyTime const & duration
 	case AnyTime::Samples:
 		return duration.samples;
 		break;
+
+	case AnyTime::BBT_Offset:
+		fatal << X_("programming error: Session::any_duration_to_samples() called with BBT_Offset\n") << endmsg;
+		/*NOTREACHED*/
+		break;
 	}
 
 	return duration.samples;