diff --git a/src/Waveform.cpp b/src/Waveform.cpp
index d67ee07ff127a4920e1208dd1ee392c886fe3a51..b2b5359d82f8dd38a374019ccad0838e2ab217ec 100644
--- a/src/Waveform.cpp
+++ b/src/Waveform.cpp
@@ -92,9 +92,9 @@ std::ostringstream oss;
 
 //- FOR DEBUG : comment out Timer and STD::COUT !!
 yat::Timer t;
-std::size_t time_to_write_data;
-std::size_t time_to_read_data;
-std::size_t time_to_copy_data;
+double time_to_write_data;
+double time_to_read_data;
+double time_to_copy_data;
 
 oss << "WaveForm_data::get_waveform_data( ) -> ENTERING ..." << std::endl;