diff --git a/server/skillhub-domain/src/main/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidator.java b/server/skillhub-domain/src/main/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidator.java
index 46e2d004..d3966ca5 100644
--- a/server/skillhub-domain/src/main/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidator.java
+++ b/server/skillhub-domain/src/main/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidator.java
@@ -8,6 +8,7 @@ import com.iflytek.skillhub.domain.skill.metadata.SkillMetadataParser;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -64,7 +65,7 @@ public class SkillPackageValidator {
         this.maxSingleFileSize = maxSingleFileSize;
         this.maxTotalPackageSize = maxTotalPackageSize;
         this.allowedExtensions = allowedExtensions.stream()
-                .map(String::toLowerCase)
+                .map(extension -> extension.toLowerCase(Locale.ROOT))
                 .collect(java.util.stream.Collectors.toUnmodifiableSet());
     }
 
@@ -138,7 +139,8 @@ public class SkillPackageValidator {
     }
 
     private boolean hasAllowedExtension(String normalizedPath) {
-        return allowedExtensions.stream().anyMatch(normalizedPath::endsWith);
+        String lowercasePath = normalizedPath.toLowerCase(Locale.ROOT);
+        return allowedExtensions.stream().anyMatch(lowercasePath::endsWith);
     }
 
     private String formatMetadataError(LocalizedDomainException exception) {
diff --git a/server/skillhub-domain/src/test/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidatorTest.java b/server/skillhub-domain/src/test/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidatorTest.java
index 43c49c02..8314050b 100644
--- a/server/skillhub-domain/src/test/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidatorTest.java
+++ b/server/skillhub-domain/src/test/java/com/iflytek/skillhub/domain/skill/validation/SkillPackageValidatorTest.java
@@ -6,6 +6,7 @@ import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Set;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -103,6 +104,23 @@ class SkillPackageValidatorTest {
         assertTrue(result.warnings().stream().anyMatch(e -> e.contains("Disallowed file extension") && e.contains("malware.exe")));
     }
 
+    @Test
+    void acceptsAllowedExtensionRegardlessOfFilenameCase() {
+        SkillPackageValidator customValidator = new SkillPackageValidator(
+                new SkillMetadataParser(), 100, SkillPackagePolicy.MAX_SINGLE_FILE_SIZE,
+                SkillPackagePolicy.MAX_TOTAL_PACKAGE_SIZE, Set.of(".md", "Makefile"));
+        List<PackageEntry> entries = List.of(
+                skillMdEntry(),
+                new PackageEntry("Makefile", "build:\n".getBytes(), 7, "text/plain")
+        );
+
+        ValidationResult result = customValidator.validate(entries);
+
+        assertTrue(result.passed());
+        assertTrue(result.warnings().stream()
+                .noneMatch(warning -> warning.contains("Disallowed file extension: Makefile")));
+    }
+
     @Test
     void testFileTooLarge() {
         // Use a custom validator with 1KB single file limit to test the logic