diff --git a/pom.xml b/pom.xml
index 35c77bcc..333d898a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -36,6 +36,7 @@
 		<java-diff-utils.version>4.10</java-diff-utils.version>
 		<grpc.version>1.45.1</grpc.version>
 		<protobuf.version>3.19.4</protobuf.version>
+		<simplemagic.version>1.17</simplemagic.version>
 	</properties>
 	<build>
 		<sourceDirectory>src/main/java</sourceDirectory>
@@ -728,5 +729,10 @@
 			<artifactId>protobuf-java</artifactId>
 			<version>${protobuf.version}</version>
 		</dependency>
+		<dependency>
+			<groupId>com.j256.simplemagic</groupId>
+			<artifactId>simplemagic</artifactId>
+			<version>${simplemagic.version}</version>
+		</dependency>
 	</dependencies>
 </project>
diff --git a/src/main/java/org/qortal/api/resource/ArbitraryResource.java b/src/main/java/org/qortal/api/resource/ArbitraryResource.java
index 73212e85..84e2d3b0 100644
--- a/src/main/java/org/qortal/api/resource/ArbitraryResource.java
+++ b/src/main/java/org/qortal/api/resource/ArbitraryResource.java
@@ -1,6 +1,8 @@
 package org.qortal.api.resource;
 
 import com.google.common.primitives.Bytes;
+import com.j256.simplemagic.ContentInfo;
+import com.j256.simplemagic.ContentInfoUtil;
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.Parameter;
 import io.swagger.v3.oas.annotations.media.ArraySchema;
@@ -12,8 +14,6 @@ import io.swagger.v3.oas.annotations.security.SecurityRequirement;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
 import java.io.*;
-import java.net.FileNameMap;
-import java.net.URLConnection;
 import java.nio.file.Files;
 import java.nio.file.Paths;
 import java.util.ArrayList;
@@ -1394,8 +1394,10 @@ public class ArbitraryResource {
 			String[] files = ArrayUtils.removeElement(outputPath.toFile().list(), ".qortal");
 			if (files.length == 1) {
 				String filename = files[0];
-				FileNameMap fileNameMap = URLConnection.getFileNameMap();
-				String mimeType = fileNameMap.getContentTypeFor(filename);
+				java.nio.file.Path filePath = Paths.get(outputPath.toString(), files[0]);
+				ContentInfoUtil util = new ContentInfoUtil();
+				ContentInfo info = util.findMatch(filePath.toFile());
+				String mimeType = (info != null) ? info.getMimeType() : null;
 				fileProperties.filename = filename;
 				fileProperties.mimeType = mimeType;
 			}