diff --git a/lib/AudioGroupData.cpp b/lib/AudioGroupData.cpp
index 18c5e08..9a29713 100644
--- a/lib/AudioGroupData.cpp
+++ b/lib/AudioGroupData.cpp
@@ -38,6 +38,7 @@ IntrusiveAudioGroupData& IntrusiveAudioGroupData::operator=(IntrusiveAudioGroupD
     m_pool = other.m_pool;
     m_sdir = other.m_sdir;
     m_samp = other.m_samp;
+    m_fmt = other.m_fmt;
 
     return *this;
 }