diff --git a/awscli/customizations/binaryformat.py b/awscli/customizations/binaryformat.py
index dd8f4c7021fd..936ce19fe9be 100644
--- a/awscli/customizations/binaryformat.py
+++ b/awscli/customizations/binaryformat.py
@@ -56,7 +56,7 @@ def _visit_scalar(self, parent, shape, name, value):
         if shape.type_name != 'blob' or not isinstance(value, six.text_type):
             return
         try:
-            parent[name] = base64.b64decode(value)
+            parent[name] = base64.b64decode(value, validate=True)
         except (binascii.Error, TypeError):
             raise InvalidBase64Error('Invalid base64: "%s"' % value)