diff --git a/src/Hydrator.php b/src/Hydrator.php
index c4797e4..ef7730e 100644
--- a/src/Hydrator.php
+++ b/src/Hydrator.php
@@ -154,23 +154,30 @@ public function hydrate(array $data, Model $model)
             $columnName = $column;
             $steps = explode('_', $column);
             $baseTable = array_shift($steps);
+            while (! empty($steps) && $baseTable !== $model->getTableAlias()) {
+                $baseTable .= '_' . array_shift($steps);
+            }
 
             $subject = $model;
             $target = $this->query->getModel();
             $stepsTaken = [];
-            foreach ($steps as $step) {
+            for ($i = 0; $i < count($steps); $i++) {
+                $step = $steps[$i];
                 $stepsTaken[] = $step;
                 $relationPath = "$baseTable." . implode('.', $stepsTaken);
 
                 try {
                     $relation = $this->query->getResolver()->resolveRelation($relationPath);
-                } catch (InvalidArgumentException $_) {
-                    // The base table is missing, which means the alias hasn't been qualified and is custom defined
-                    break;
                 } catch (InvalidRelationException $_) {
-                    array_pop($stepsTaken);
-                    $columnName = implode('_', array_slice($steps, count($stepsTaken)));
-                    break;
+                    if (isset($steps[$i + 1])) {
+                        $steps[$i + 1] = $step . '_' . $steps[$i + 1];
+                        array_pop($stepsTaken);
+                        continue;
+                    } else {
+                        array_pop($stepsTaken);
+                        $columnName = implode('_', array_slice($steps, $i));
+                        break;
+                    }
                 }
 
                 if (! $subject->hasProperty($step)) {
diff --git a/tests/HydratorTest.php b/tests/HydratorTest.php
index 0bd6bc2..cbcfe6c 100644
--- a/tests/HydratorTest.php
+++ b/tests/HydratorTest.php
@@ -46,4 +46,45 @@ public function testWhetherProperlyQualifiedColumnsAreOnlyPassedOnToMatchingTarg
             'Properly qualified relation columns are spilled onto the base model'
         );
     }
+
+    public function testCustomAliasesForTheBaseTableAndRelationsWithUnderscoresInTheirNameAreProperlyHydrated()
+    {
+        $query = CarUser::on(new TestConnection())
+            ->with('user');
+
+        $hydrator = $query->createHydrator();
+
+        $subject = new CarUser();
+        $hydrator->hydrate(['car_user_definitely' => 'custom'], $subject);
+
+        $this->assertTrue(
+            isset($subject->definitely),
+            'Custom aliases for the base table are not correctly'
+            . ' hydrated if the table name contains an underscore'
+        );
+        $this->assertSame(
+            'custom',
+            $subject->definitely,
+            'Custom aliases for the base table are not correctly'
+            . ' hydrated if the table name contains an underscore'
+        );
+
+        $query = User::on(new TestConnection())
+            ->with('user_custom_keys');
+
+        $hydrator = $query->createHydrator();
+
+        $subject = new User();
+        $hydrator->hydrate(['user_user_custom_keys_definitely' => 'custom'], $subject);
+
+        $this->assertTrue(
+            isset($subject->user_custom_keys->definitely),
+            'Custom aliases for relations are not correctly hydrated if their name contains an underscore'
+        );
+        $this->assertSame(
+            'custom',
+            $subject->user_custom_keys->definitely,
+            'Custom aliases for relations are not correctly hydrated if their name contains an underscore'
+        );
+    }
 }
diff --git a/tests/User.php b/tests/User.php
index afcbf3a..20e33ec 100644
--- a/tests/User.php
+++ b/tests/User.php
@@ -38,5 +38,8 @@ public function createRelations(Relations $relations)
 
         $relations->belongsToMany('car', Car::class)
             ->through(CarUser::class);
+
+        $relations->belongsToMany('user_custom_keys', Car::class)
+            ->through(CarUserWithCustomKeys::class);
     }
 }