diff --git a/gerbview/excellon_image.h b/gerbview/excellon_image.h
index 84bc736d4b..cb24e0c6ec 100644
--- a/gerbview/excellon_image.h
+++ b/gerbview/excellon_image.h
@@ -142,11 +142,10 @@ public: EXCELLON_IMAGE( int layer ) :
 
     ~EXCELLON_IMAGE() {};
 
-    virtual void ResetDefaultValues() override
-    {
-        GERBER_FILE_IMAGE::ResetDefaultValues();
-        SelectUnits( false );
-    }
+    /**
+     * Set all parameters to a default value, before reading a file
+     */
+    virtual void ResetDefaultValues() override;
 
 
     /**
diff --git a/gerbview/excellon_read_drill_file.cpp b/gerbview/excellon_read_drill_file.cpp
index b9adc21159..4b1ce3ee3f 100644
--- a/gerbview/excellon_read_drill_file.cpp
+++ b/gerbview/excellon_read_drill_file.cpp
@@ -293,6 +293,19 @@ bool GERBVIEW_FRAME::Read_EXCELLON_File( const wxString& aFullFileName )
     return success;
 }
 
+
+void EXCELLON_IMAGE::ResetDefaultValues()
+{
+    GERBER_FILE_IMAGE::ResetDefaultValues();
+    SelectUnits( false );       // Default unit = inch
+
+    // Files using non decimal can use No Trailing zeros or No leading Zeros
+    // Unfortunately, the identifier (INCH,TZ or INCH,LZ for instance) is not
+    // always set in drill files.
+    // The option leading zeros looks like more frequent, so use this default
+    m_NoTrailingZeros = true;
+}
+
 /*
  * Read a EXCELLON file.
  * Gerber classes are used because there is likeness between Gerber files
@@ -305,7 +318,6 @@ bool GERBVIEW_FRAME::Read_EXCELLON_File( const wxString& aFullFileName )
  *   integer 2.4 format in imperial units,
  *   integer 3.2 or 3.3 format (metric units).
  */
-
 bool EXCELLON_IMAGE::LoadFile( const wxString & aFullFileName )
 {
     // Set the default parameter values:
@@ -473,8 +485,7 @@ bool EXCELLON_IMAGE::Execute_HEADER_And_M_Command( char*& text )
         if( *text != ',' )
         {
             // No TZ or LZ specified. Should be a decimal format
-            // but this is not always the case. Use default TZ setting as default
-            m_NoTrailingZeros = false;
+            // but this is not always the case. Use our default setting
             break;
         }
 
diff --git a/gerbview/gerber_file_image.h b/gerbview/gerber_file_image.h
index 45d660b60c..348448a894 100644
--- a/gerbview/gerber_file_image.h
+++ b/gerbview/gerber_file_image.h
@@ -135,6 +135,9 @@ public:
      */
     int GetDcodesCount();
 
+    /**
+     * Set all parameters to a default value, before reading a file
+     */
     virtual void ResetDefaultValues();
 
     COLOR4D GetPositiveDrawColor() const { return m_PositiveDrawColor; }