diff --git a/src/nwb/RecordingContainers.cpp b/src/nwb/RecordingContainers.cpp
index cd2b96c5..59b01bfb 100644
--- a/src/nwb/RecordingContainers.cpp
+++ b/src/nwb/RecordingContainers.cpp
@@ -79,8 +79,3 @@ Status RecordingContainers::writeSpikeEventData(const SizeType& containerInd,
 
   ses->writeSpike(numSamples, numChannels, data, timestamps);
 }
-
-SizeType RecordingContainers::size()
-{
-  return m_containers.size();
-}
\ No newline at end of file
diff --git a/src/nwb/RecordingContainers.hpp b/src/nwb/RecordingContainers.hpp
index 6b47056f..0ffd938d 100644
--- a/src/nwb/RecordingContainers.hpp
+++ b/src/nwb/RecordingContainers.hpp
@@ -108,7 +108,7 @@ class RecordingContainers
   /**
    * @brief Get the number of recording containers
    */
-  SizeType size();
+  inline SizeType size() const { return m_containers.size(); }
 
 private:
   /**