diff --git a/libs/ardour/midi_buffer.cc b/libs/ardour/midi_buffer.cc
index 6707465c44..d0e9882aeb 100644
--- a/libs/ardour/midi_buffer.cc
+++ b/libs/ardour/midi_buffer.cc
@@ -442,15 +442,15 @@ MidiBuffer::merge_in_place (const MidiBuffer &other)
 		return true;
 	}
 
+	if (size() + other.size() > _capacity) {
+		return false;
+	}
+
 	if (size() == 0) {
 		copy (other);
 		return true;
 	}
 
-	if (size() + other.size() > _capacity) {
-		return false;
-	}
-
 	const_iterator them = other.begin();
 	iterator us = begin();