diff --git a/app/V1Module/presenters/ExercisesConfigPresenter.php b/app/V1Module/presenters/ExercisesConfigPresenter.php
index 2fec70812..50643002e 100644
--- a/app/V1Module/presenters/ExercisesConfigPresenter.php
+++ b/app/V1Module/presenters/ExercisesConfigPresenter.php
@@ -653,12 +653,10 @@ public function actionSetScoreConfig(string $id) {
 
     // validate score configuration
     $calculator = $this->calculators->getCalculator($exercise->getScoreCalculator());
-    if (!$calculator->isScoreConfigValid($config)) {
-      throw new ExerciseConfigException("Exercise score configuration is not valid");
-    }
+    $normalizedConfig = $calculator->validateAndNormalizeScore($config);  // throws if validation fails
 
     $exercise->updatedNow();
-    $exercise->setScoreConfig($config);
+    $exercise->setScoreConfig($normalizedConfig);
     $this->exercises->flush();
 
     // check exercise configuration
diff --git a/app/helpers/Evaluation/ScoreCalculators/IScoreCalculator.php b/app/helpers/Evaluation/ScoreCalculators/IScoreCalculator.php
index deecfb3f3..c5e7d52b7 100644
--- a/app/helpers/Evaluation/ScoreCalculators/IScoreCalculator.php
+++ b/app/helpers/Evaluation/ScoreCalculators/IScoreCalculator.php
@@ -2,6 +2,7 @@
 
 namespace App\Helpers\Evaluation;
 use App\Exceptions\SubmissionEvaluationFailedException;
+use App\Exceptions\ExerciseConfigException;
 
 /**
  * Interface for score computations. Purpose is to merge scores of all
@@ -24,6 +25,15 @@ public function computeScore(string $scoreConfig, array $testResults): float;
    */
   public function isScoreConfigValid(string $scoreConfig): bool;
 
+  /**
+   * Performs validation and normalization on config string.
+   * This should be used instead of validation when the score config is processed as API input.
+   * @param string $scoreConfig YAML configuration for the score calculator
+   * @return string Normalized and polished YAML with score configuration
+   * @throws ExerciseConfigException
+   */
+  public function validateAndNormalizeScore(string $scoreConfig): string;
+
   /**
    * Make default configuration for array of test names. Each test will
    * have the same priority as others.
diff --git a/app/helpers/Evaluation/ScoreCalculators/SimpleScoreCalculator.php b/app/helpers/Evaluation/ScoreCalculators/SimpleScoreCalculator.php
index f1fd42593..089bc378e 100644
--- a/app/helpers/Evaluation/ScoreCalculators/SimpleScoreCalculator.php
+++ b/app/helpers/Evaluation/ScoreCalculators/SimpleScoreCalculator.php
@@ -3,6 +3,7 @@
 namespace App\Helpers\Evaluation;
 
 use App\Exceptions\SubmissionEvaluationFailedException;
+use App\Exceptions\ExerciseConfigException;
 use App\Helpers\Evaluation\IScoreCalculator;
 use Symfony\Component\Yaml\Yaml;
 use Symfony\Component\Yaml\Exception\ParseException;
@@ -17,6 +18,32 @@
  * weights can be arbitrary, what matters are ratios.
  */
 class SimpleScoreCalculator implements IScoreCalculator {
+  /**
+   * Internal function that safely retrieves score config weights.
+   * @param string $scoreConfig
+   * @return array|null Null if the config is invalid, name => weight array otherwise.
+   */
+  private function getTestWeights(string $scoreConfig): ?array {
+    try {
+      $config = Yaml::parse($scoreConfig);
+      $normalizedWeights = [];
+
+      if (isset($config['testWeights']) && is_array($config['testWeights'])) {
+        foreach ($config['testWeights'] as $name => $value) {
+          if (!is_integer($value)) {
+            return null;
+          }
+          $normalizedWeights[trim($name)] = $value;
+        }
+      } else {
+        return null;
+      }
+    } catch (ParseException $e) {
+      return null;
+    }
+
+    return $normalizedWeights;
+  }
 
   /**
    * Function that computes the resulting score from simple YML config and test results score
@@ -26,13 +53,11 @@ class SimpleScoreCalculator implements IScoreCalculator {
    * @throws SubmissionEvaluationFailedException
    */
   public function computeScore(string $scoreConfig, array $testResults): float {
-    if (!$this->isScoreConfigValid($scoreConfig)) {
+    $weights = $this->getTestWeights($scoreConfig);
+    if ($weights === null) {
       throw new SubmissionEvaluationFailedException("Assignment score configuration is invalid");
     }
 
-    $config = Yaml::parse($scoreConfig);
-    $weights = $config['testWeights'];
-
     // assign zero ratio to all tests which does not have specified value
     foreach ($testResults as $name => $score) {
       if (!array_key_exists($name, $weights)) {
@@ -57,23 +82,22 @@ public function computeScore(string $scoreConfig, array $testResults): float {
    * @return bool If the configuration is valid or not
    */
   public function isScoreConfigValid(string $scoreConfig): bool {
-    try {
-      $config = Yaml::parse($scoreConfig);
+    return $this->getTestWeights($scoreConfig) !== null;
+  }
 
-      if (isset($config['testWeights']) && is_array($config['testWeights'])) {
-        foreach ($config['testWeights'] as $value) {
-          if (!is_integer($value)) {
-            return false;
-          }
-        }
-      } else {
-        return false;
-      }
-    } catch (ParseException $e) {
-      return false;
+  /**
+   * Performs validation and normalization on config string.
+   * This should be used instead of validation when the score config is processed as API input.
+   * @param string $scoreConfig YAML configuration for the score calculator
+   * @return string Normalized and polished YAML with score configuration
+   * @throws ExerciseConfigException
+   */
+  public function validateAndNormalizeScore(string $scoreConfig): string {
+    $weights = $this->getTestWeights($scoreConfig);
+    if ($weights === null) {
+      throw new ExerciseConfigException("Exercise score configuration is not valid");
     }
-
-    return true;
+    return Yaml::dump([ 'testWeights' => $weights ]);
   }
 
   /**
diff --git a/tests/Presenters/ExercisesConfigPresenter.phpt b/tests/Presenters/ExercisesConfigPresenter.phpt
index 29e80c2de..ab1c7ca66 100644
--- a/tests/Presenters/ExercisesConfigPresenter.phpt
+++ b/tests/Presenters/ExercisesConfigPresenter.phpt
@@ -9,6 +9,7 @@ use App\Model\Entity\ExerciseTest;
 use App\Model\Entity\HardwareGroup;
 use App\V1Module\Presenters\ExercisesConfigPresenter;
 use Tester\Assert;
+use Symfony\Component\Yaml\Yaml;
 
 /**
  * @testCase
@@ -515,8 +516,9 @@ class TestExercisesConfigPresenter extends Tester\TestCase
     $result = $response->getPayload();
     Assert::equal(200, $result['code']);
 
-    $payload = $result['payload'];
-    Assert::equal("testWeights:\n  \"Test 1\": 100\n  \"Test 2\": 100\n  \"Test 3\": 100", $payload);
+    $payload = Yaml::parse($result['payload']);
+    $expected = Yaml::parse($config);
+    Assert::equal($expected, $payload);
   }
 
   public function testGetTests() {