diff --git a/src/daemon/judge/judger-base.ts b/src/daemon/judge/judger-base.ts
index 1f6c25b..ec94bde 100644
--- a/src/daemon/judge/judger-base.ts
+++ b/src/daemon/judge/judger-base.ts
@@ -71,7 +71,7 @@ export abstract class JudgerBase {
                                 currentTaskResult.errorMessage = err.toString();
                                 winston.warn(`Task runner error: ${err.toString()} (subtask ${subtaskIndex}, case ${index})`);
                             }
-                            if (score === 0 || score === NaN) {
+                            if (score == null || isNaN(score) || score === 0) {
                                 winston.debug(`Subtask ${subtaskIndex}, case ${index}: zero, skipping the rest.`);
                                 skipped = true;
                             }
diff --git a/src/runner/judge.ts b/src/runner/judge.ts
index 1c2d954..ca2b31c 100644
--- a/src/runner/judge.ts
+++ b/src/runner/judge.ts
@@ -46,7 +46,7 @@ async function runSpj(spjBinDir: string, spjLanguage: Language): Promise<SpjResu
             score = Number(scoreString);
         const messageString = await readFileLength(pathLib.join(spjWorkingDir, messageFileName), Cfg.stderrDisplayLimit);
 
-        if ((!scoreString) || score === NaN || score < 0 || score > spjFullScore) {
+        if ((!scoreString) || isNaN(score) || score < 0 || score > spjFullScore) {
             return {
                 status: TestcaseResultType.JudgementFailed,
                 message: `Special Judge returned an unrecoginzed score: ${scoreString}.`,