diff --git a/eeschema/dialogs/dialog_sheet_properties.cpp b/eeschema/dialogs/dialog_sheet_properties.cpp
index e3935c3a4c..1eff396706 100644
--- a/eeschema/dialogs/dialog_sheet_properties.cpp
+++ b/eeschema/dialogs/dialog_sheet_properties.cpp
@@ -249,8 +249,6 @@ bool DIALOG_SHEET_PROPERTIES::TransferDataFromWindow()
 
     // Ensure filepath is not empty.  (In normal use will be caught by grid validators,
     // but unedited data from existing files can be bad.)
-
-    // @todo What happens when there are invalid file name characters?
     if( newRelativeNativeFilename.IsEmpty() )
     {
         wxMessageBox( _( "A sheet must have a valid file name." ) );
@@ -614,16 +612,6 @@ void DIALOG_SHEET_PROPERTIES::OnGridCellChanging( wxGridEvent& event )
             wxMessageBox( _( "A sheet must have a file specified." ) );
             success = false;
         }
-        else
-        {
-            wxFileName fn = textControl->GetValue();
-
-            if( fn.GetExt().CmpNoCase( KiCadSchematicFileExtension ) != 0 )
-            {
-                wxMessageBox( _( "Sheet filename must have a '.kicad_sch' extension." ) );
-                success = false;
-            }
-        }
     }
 
     if( success && control && control->GetValidator() )
diff --git a/eeschema/fields_grid_table.cpp b/eeschema/fields_grid_table.cpp
index 8ea8a71229..c2ab4729c8 100644
--- a/eeschema/fields_grid_table.cpp
+++ b/eeschema/fields_grid_table.cpp
@@ -471,7 +471,24 @@ void FIELDS_GRID_TABLE<T>::SetValue( int aRow, int aCol, const wxString &aValue
         break;
 
     case FDC_VALUE:
-        field.SetText( aValue );
+    {
+        wxString value( aValue );
+
+        if( m_parentType == SCH_SHEET_T && aRow == SHEETFILENAME )
+        {
+            wxFileName fn( value );
+
+            // It's annoying to throw up nag dialogs when the extension isn't right.  Just
+            // fix it.
+            if( fn.GetExt().CmpNoCase( KiCadSchematicFileExtension ) != 0 )
+            {
+                fn.SetExt( KiCadSchematicFileExtension );
+                value = fn.GetFullPath();
+            }
+        }
+
+        field.SetText( value );
+    }
         break;
 
     case FDC_SHOWN:
diff --git a/eeschema/sch_validators.cpp b/eeschema/sch_validators.cpp
index 7f153086ea..a12815a567 100644
--- a/eeschema/sch_validators.cpp
+++ b/eeschema/sch_validators.cpp
@@ -87,7 +87,7 @@ SCH_FIELD_VALIDATOR::SCH_FIELD_VALIDATOR( const SCH_FIELD_VALIDATOR& aValidator
 bool SCH_FIELD_VALIDATOR::Validate( wxWindow *aParent )
 {
     // If window is disabled, simply return
-    if( !m_validatorWindow->IsEnabled() || !m_validatorWindow->IsShown() )
+    if( !m_validatorWindow->IsEnabled() )
         return true;
 
     wxTextEntry * const text = GetTextEntry();