diff --git a/src/LocalDateTime.php b/src/LocalDateTime.php
index a9ad6b99..927910b1 100644
--- a/src/LocalDateTime.php
+++ b/src/LocalDateTime.php
@@ -426,7 +426,10 @@ public function plusDuration(Duration $duration): LocalDateTime
             return $this;
         }
 
-        $days = Math::floorDiv($this->time->toSecondOfDay() + $duration->getSeconds(), LocalTime::SECONDS_PER_DAY);
+        $seconds = $this->time->toSecondOfDay() + $duration->getSeconds()
+            + intdiv($this->time->getNano() + $duration->getNanos(), LocalTime::NANOS_PER_SECOND);
+
+        $days = Math::floorDiv($seconds, LocalTime::SECONDS_PER_DAY);
 
         return new LocalDateTime($this->date->plusDays($days), $this->time->plusDuration($duration));
     }
diff --git a/tests/LocalDateTimeTest.php b/tests/LocalDateTimeTest.php
index 8eedf007..4c1c4716 100644
--- a/tests/LocalDateTimeTest.php
+++ b/tests/LocalDateTimeTest.php
@@ -701,6 +701,8 @@ public static function providerDuration(): array
             [7654321, 1999999999, 2001, 5, 2, 18, 17, 9, 123456788],
             [-654321, -987654321, 2001, 1, 26, 14, 19, 44, 135802468],
             [-7654321, 2013456789, 2000, 11, 6, 13, 53, 7, 136913578],
+            [71693, 900000000, 2001, 2, 4, 0, 0, 0, 23456789],
+            [-14707, 900000000, 2001, 2, 3, 0, 0, 0, 23456789],
         ];
     }