diff --git a/app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupDecoder.kt b/app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupDecoder.kt
index 34f862548..55553082f 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupDecoder.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupDecoder.kt
@@ -3,18 +3,21 @@ package eu.kanade.tachiyomi.data.backup
 import android.content.Context
 import android.net.Uri
 import eu.kanade.tachiyomi.data.backup.models.Backup
+import kotlinx.serialization.SerializationException
 import kotlinx.serialization.protobuf.ProtoBuf
 import okio.buffer
 import okio.gzip
 import okio.source
+import tachiyomi.core.common.i18n.stringResource
+import tachiyomi.i18n.MR
 import uy.kohesive.injekt.Injekt
 import uy.kohesive.injekt.api.get
+import java.io.IOException
 
 class BackupDecoder(
     private val context: Context,
     private val parser: ProtoBuf = Injekt.get(),
 ) {
-
     /**
      * Decode a potentially-gzipped backup.
      */
@@ -26,13 +29,25 @@ class BackupDecoder(
                 require(2)
             }
             val id1id2 = peeked.readShort()
-            val backupString = if (id1id2.toInt() == 0x1f8b) { // 0x1f8b is gzip magic bytes
-                source.gzip().buffer()
-            } else {
-                source
+            val backupString = when (id1id2.toInt()) {
+                0x1f8b -> source.gzip().buffer() // 0x1f8b is gzip magic bytes
+                MAGIC_JSON_SIGNATURE1, MAGIC_JSON_SIGNATURE2, MAGIC_JSON_SIGNATURE3 -> {
+                    throw IOException(context.stringResource(MR.strings.invalid_backup_file_json))
+                }
+                else -> source
             }.use { it.readByteArray() }
 
-            parser.decodeFromByteArray(Backup.serializer(), backupString)
+            try {
+                parser.decodeFromByteArray(Backup.serializer(), backupString)
+            } catch (_: SerializationException) {
+                throw IOException(context.stringResource(MR.strings.invalid_backup_file_unknown))
+            }
         }
     }
+
+    companion object {
+        private const val MAGIC_JSON_SIGNATURE1 = 0x7b7d // `{}`
+        private const val MAGIC_JSON_SIGNATURE2 = 0x7b22 // `{"`
+        private const val MAGIC_JSON_SIGNATURE3 = 0x7b0a // `{\n`
+    }
 }
diff --git a/i18n/src/commonMain/moko-resources/base/strings.xml b/i18n/src/commonMain/moko-resources/base/strings.xml
index 08bbe2d76..73f7d4a6e 100644
--- a/i18n/src/commonMain/moko-resources/base/strings.xml
+++ b/i18n/src/commonMain/moko-resources/base/strings.xml
@@ -518,6 +518,8 @@
     <string name="invalid_backup_file">Invalid backup file:</string>
     <string name="invalid_backup_file_error">Full error:</string>
     <string name="invalid_backup_file_missing_manga">Backup does not contain any library entries.</string>
+    <string name="invalid_backup_file_json">JSON backup not supported</string>
+    <string name="invalid_backup_file_unknown">Backup file is corrupted</string>
     <string name="backup_restore_missing_sources">Missing sources:</string>
     <string name="backup_restore_missing_trackers">Trackers not logged into:</string>
     <string name="backup_restore_content_full">You may need to install any missing extensions and log in to tracking services afterwards to use them.</string>