diff --git a/browser/common.py b/browser/common.py
index fd98c66..dcc964d 100644
--- a/browser/common.py
+++ b/browser/common.py
@@ -217,7 +217,7 @@ class BaseView(GenericView, I18NView):
         self.skin = skin
 
     @Lazy
-    def modified(self):
+    def modifiedRaw(self):
         """ get date/time of last modification
         """
         d = getattr(self.adapted, 'modified', None)
@@ -226,6 +226,11 @@ class BaseView(GenericView, I18NView):
             d = dc.modified or dc.created
         if isinstance(d, str):
             d = datetime(*(strptime(d, '%Y-%m-%dT%H:%M')[:6]))
+        return d
+
+    @Lazy
+    def modified(self):
+        d = self.modifiedRaw
         return d and d.strftime('%Y-%m-%d %H:%M') or ''
 
     @Lazy
diff --git a/browser/resource.py b/browser/resource.py
index c5d6afa..ba3f53c 100644
--- a/browser/resource.py
+++ b/browser/resource.py
@@ -176,6 +176,9 @@ class ResourceView(BaseView):
 
     def show(self, useAttachment=False):
         """ show means: "download"..."""
+        # TODO: control access, e.g. to protected images
+        # if self.adapted.isProtected():
+        #     raise Unauthorized()
         context = self.context
         self.recordAccess('show', target=self.uniqueId)
         ti = IType(context).typeInterface
@@ -194,6 +197,13 @@ class ResourceView(BaseView):
             response.setHeader('Content-Type', 'text/html')
             return self.renderText(data, ct)
         response.setHeader('Content-Type', ct)
+        # set Last-Modified header
+        modified = self.modifiedRaw
+        if modified:
+            format = '%a, %d %b %Y %H:%M:%S %Z'
+            if modified.tzinfo is None:
+                format = format[:-3] + ' GMT'
+            response.setHeader('Last-Modified', modified.strftime(format))
         return data
 
     def renderText(self, text, contentType):