diff --git a/common/common_plotGERBER_functions.cpp b/common/common_plotGERBER_functions.cpp
index 6c5b07bcfb..a13064b5db 100644
--- a/common/common_plotGERBER_functions.cpp
+++ b/common/common_plotGERBER_functions.cpp
@@ -43,6 +43,9 @@ void GERBER_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
     plotScale = 1;              // Plot scale is *always* 1.0
 
     m_IUsPerDecimil = aIusPerDecimil;
+    // gives now a default value to iuPerDeviceUnit (because the units of the caller is now known)
+    // which could be modified later by calling SetGerberCoordinatesFormat()
+    iuPerDeviceUnit = pow( 10.0, m_gerberUnitFmt ) / ( m_IUsPerDecimil * 10000.0 );
 
     // We don't handle the filmbox, and it's more useful to keep the
     // origin at the origin
diff --git a/pcbnew/exporters/gen_drill_report_files.cpp b/pcbnew/exporters/gen_drill_report_files.cpp
index 7c474553c3..5a2c6ad5fb 100644
--- a/pcbnew/exporters/gen_drill_report_files.cpp
+++ b/pcbnew/exporters/gen_drill_report_files.cpp
@@ -78,6 +78,7 @@ bool EXCELLON_WRITER::GenDrillMapFile( const wxString& aFullFileName,
         offset  = GetOffset();
         plotter = new GERBER_PLOTTER();
         plotter->SetViewport( offset, IU_PER_DECIMILS, scale, false );
+        plotter->SetGerberCoordinatesFormat( 5 );   // format x.5 unit = mm
         break;
 
     case PLOT_FORMAT_HPGL:    // Scale for HPGL format.