diff --git a/bigchaindb/common/exceptions.py b/bigchaindb/common/exceptions.py
index 4b95f84b..76513010 100644
--- a/bigchaindb/common/exceptions.py
+++ b/bigchaindb/common/exceptions.py
@@ -42,6 +42,11 @@ class OperationError(BigchainDBError):
 
 ################################################################################
 # Validation errors
+#
+# All validation errors (which are handleable errors, not faults) should
+# subclass ValidationError. However, where possible they should also have their
+# own distinct type to differentiate them from other validation errors,
+# especially for the purposes of testing.
 
 
 class ValidationError(BigchainDBError):
diff --git a/bigchaindb/pipelines/block.py b/bigchaindb/pipelines/block.py
index 2a43686a..b1d6cdee 100644
--- a/bigchaindb/pipelines/block.py
+++ b/bigchaindb/pipelines/block.py
@@ -76,7 +76,7 @@ class BlockPipeline:
             tx.validate(self.bigchain)
             return tx
         except ValidationError as e:
-            # todo: log
+            logger.warning('Invalid tx: %s' % e)
             self.bigchain.delete_transaction(tx.id)
             return None
 
diff --git a/bigchaindb/pipelines/vote.py b/bigchaindb/pipelines/vote.py
index 088c4eac..0431e20b 100644
--- a/bigchaindb/pipelines/vote.py
+++ b/bigchaindb/pipelines/vote.py
@@ -108,8 +108,8 @@ class Vote:
         try:
             tx.validate(self.bigchain)
             valid = True
-        except exceptions.ValidationError:
-            # TODO: log
+        except exceptions.ValidationError as e:
+            logger.warning('Invalid tx: %s' % e)
             valid = False
 
         return valid, block_id, num_tx
diff --git a/tests/pipelines/test_vote.py b/tests/pipelines/test_vote.py
index aaa184f0..fa167d17 100644
--- a/tests/pipelines/test_vote.py
+++ b/tests/pipelines/test_vote.py
@@ -128,7 +128,7 @@ def test_validate_block_with_invalid_signature(b):
 @pytest.mark.genesis
 def test_vote_validate_transaction(b):
     from bigchaindb.pipelines import vote
-    from bigchaindb.models import Transaction
+    from bigchaindb.common.exceptions import ValidationError
 
     tx = dummy_tx(b)
     vote_obj = vote.Vote()
@@ -147,7 +147,6 @@ def test_vote_validate_transaction(b):
             validation = vote_obj.validate_tx(tx, 456, 10)
 
 
-
 @pytest.mark.genesis
 def test_vote_accumulates_transactions(b):
     from bigchaindb.pipelines import vote