diff --git a/app/src/main/java/app/grapheneos/pdfviewer/loader/DocumentPropertiesLoader.kt b/app/src/main/java/app/grapheneos/pdfviewer/loader/DocumentPropertiesLoader.kt
index 7c9563b..cd2dd5f 100644
--- a/app/src/main/java/app/grapheneos/pdfviewer/loader/DocumentPropertiesLoader.kt
+++ b/app/src/main/java/app/grapheneos/pdfviewer/loader/DocumentPropertiesLoader.kt
@@ -9,6 +9,7 @@ import android.text.Spanned
 import android.text.format.Formatter
 import android.text.style.StyleSpan
 import android.util.Log
+import androidx.core.database.getLongOrNull
 import app.grapheneos.pdfviewer.R
 import org.json.JSONException
 
@@ -102,8 +103,9 @@ class DocumentPropertiesLoader(
 
             val indexSize: Int = cursor.getColumnIndex(OpenableColumns.SIZE)
             if (indexSize >= 0) {
-                val fileSize: Long = cursor.getString(indexSize).toLong()
-                collections[DocumentProperty.FileSize] = Formatter.formatShortFileSize(context, fileSize)
+                val fileSize = cursor.getLongOrNull(indexSize)
+                collections[DocumentProperty.FileSize] =
+                    fileSize?.let { Formatter.formatFileSize(context, it) } ?: context.getString(R.string.unknown_file_size)
             }
         }
         return collections
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index a129a93..55f05a2 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -44,4 +44,6 @@
     <string name="creator">Creator</string>
     <string name="pdf_version">PDF version</string>
     <string name="pages">Pages</string>
+
+    <string name="unknown_file_size">Unknown</string>
 </resources>