diff --git a/hydrus/client/db/ClientDBFilesSearch.py b/hydrus/client/db/ClientDBFilesSearch.py
index 0796faf6..6d42caa4 100644
--- a/hydrus/client/db/ClientDBFilesSearch.py
+++ b/hydrus/client/db/ClientDBFilesSearch.py
@@ -2445,6 +2445,12 @@ class ClientDBFilesQuery( ClientDBModule.ClientDBModule ):
                 
                 if sort_data == CC.SORT_FILES_BY_IMPORT_TIME:
                     
+                    def deal_with_none( x ):
+                        
+                        if x is None: return -1
+                        else: return x
+                        
+                    
                     def key( row ):
                         
                         hash_id = row[0]
@@ -2452,7 +2458,7 @@ class ClientDBFilesQuery( ClientDBModule.ClientDBModule ):
                         
                         # hash_id to differentiate files imported in the same second
                         
-                        return ( timestamp, hash_id )
+                        return ( deal_with_none( timestamp ), hash_id )
                         
                     
                 elif sort_data == CC.SORT_FILES_BY_RATIO:
diff --git a/hydrus/core/HydrusConstants.py b/hydrus/core/HydrusConstants.py
index 865d757b..d530c085 100644
--- a/hydrus/core/HydrusConstants.py
+++ b/hydrus/core/HydrusConstants.py
@@ -764,7 +764,7 @@ MIMES_WITH_THUMBNAILS = set( IMAGES ).union( ANIMATIONS ).union( VIDEO ).union(
 
 FILES_THAT_CAN_HAVE_ICC_PROFILE = { IMAGE_JPEG, IMAGE_PNG, IMAGE_GIF, IMAGE_TIFF }
 
-FILES_THAT_CAN_HAVE_EXIF = { IMAGE_JPEG, IMAGE_TIFF }
+FILES_THAT_CAN_HAVE_EXIF = { IMAGE_JPEG, IMAGE_TIFF, IMAGE_PNG }
 # images and animations that PIL can handle
 FILES_THAT_CAN_HAVE_HUMAN_READABLE_EMBEDDED_METADATA = { IMAGE_JPEG, IMAGE_PNG, IMAGE_BMP, IMAGE_WEBP, IMAGE_TIFF, IMAGE_ICON, IMAGE_GIF, IMAGE_APNG }
 
diff --git a/hydrus/core/HydrusImageHandling.py b/hydrus/core/HydrusImageHandling.py
index 0964477b..627615b1 100644
--- a/hydrus/core/HydrusImageHandling.py
+++ b/hydrus/core/HydrusImageHandling.py
@@ -529,7 +529,7 @@ def GenerateThumbnailBytesPIL( pil_image: PILImage.Image ) -> bytes:
 
 def GetEXIFDict( pil_image: PILImage.Image ) -> typing.Optional[ dict ]:
     
-    if pil_image.format in ( 'JPEG', 'TIFF' ) and hasattr( pil_image, '_getexif' ):
+    if pil_image.format in ( 'JPEG', 'TIFF', 'PNG' ) and hasattr( pil_image, '_getexif' ):
         
         try: