diff --git a/pdfminer/pdftypes.py b/pdfminer/pdftypes.py
index c7c8a0a..9c31ad9 100644
--- a/pdfminer/pdftypes.py
+++ b/pdfminer/pdftypes.py
@@ -275,7 +275,7 @@ class PDFStream(PDFObject):
             else:
                 raise PDFNotImplementedError('Unsupported filter: %r' % f)
             # apply predictors
-            if 'Predictor' in params:
+            if params and 'Predictor' in params:
                 pred = int_value(params['Predictor'])
                 if pred == 1:
                     # no predictor