diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9c7a3a06..d7cee7ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+- Gemini now tries to perform mutation on both systems regardless of
+  if one of them fail.
+
 ## [1.0.1] - 2019-05-16
 
 - Gemini ensures that primary key buckets do not overflow int32.
diff --git a/session.go b/session.go
index 6984ea32..a628a318 100644
--- a/session.go
+++ b/session.go
@@ -54,14 +54,14 @@ func (s *Session) Close() {
 	s.oracleSession.Close()
 }
 
-func (s *Session) Mutate(query string, values ...interface{}) error {
+func (s *Session) Mutate(query string, values ...interface{}) (e error) {
 	if err := s.testSession.Query(query, values...).Exec(); err != nil {
-		return fmt.Errorf("%v [cluster = test, query = '%s']", err, query)
+		e = multierr.Append(e, fmt.Errorf("%v [cluster = test, query = '%s']", err, query))
 	}
 	if err := s.oracleSession.Query(query, values...).Exec(); err != nil {
-		return fmt.Errorf("%v [cluster = oracle, query = '%s']", err, query)
+		e = multierr.Append(e, fmt.Errorf("%v [cluster = oracle, query = '%s']", err, query))
 	}
-	return nil
+	return
 }
 
 func (s *Session) Check(table Table, query string, values ...interface{}) (err error) {
@@ -69,10 +69,10 @@ func (s *Session) Check(table Table, query string, values ...interface{}) (err e
 	oracleIter := s.oracleSession.Query(query, values...).Iter()
 	defer func() {
 		if e := testIter.Close(); e != nil {
-			err = multierr.Append(err, errors.Errorf("test system failed: %s", err.Error()))
+			err = multierr.Append(err, errors.Errorf("test system failed: %s", e.Error()))
 		}
 		if e := oracleIter.Close(); e != nil {
-			err = multierr.Append(err, errors.Errorf("oracle failed: %s", err.Error()))
+			err = multierr.Append(err, errors.Errorf("oracle failed: %s", e.Error()))
 		}
 	}()