diff --git a/app/src/main/java/at/tomtasche/reader/background/CoreWrapper.java b/app/src/main/java/at/tomtasche/reader/background/CoreWrapper.java
index eeceebe9bc0c..bcecd270203a 100644
--- a/app/src/main/java/at/tomtasche/reader/background/CoreWrapper.java
+++ b/app/src/main/java/at/tomtasche/reader/background/CoreWrapper.java
@@ -107,20 +107,20 @@ public static class CoreResult {
         public String extension;
     }
 
-    public class CoreCouldNotOpenException extends RuntimeException {}
+    public static class CoreCouldNotOpenException extends RuntimeException {}
 
-    public class CoreEncryptedException extends RuntimeException {}
+    public static class CoreEncryptedException extends RuntimeException {}
 
-    public class CoreCouldNotTranslateException extends RuntimeException {}
+    public static class CoreCouldNotTranslateException extends RuntimeException {}
 
-    public class CoreUnexpectedFormatException extends RuntimeException {}
+    public static class CoreUnexpectedFormatException extends RuntimeException {}
 
-    public class CoreUnexpectedErrorCodeException extends RuntimeException {}
+    public static class CoreUnexpectedErrorCodeException extends RuntimeException {}
 
-    public class CoreUnknownErrorException extends RuntimeException {}
+    public static class CoreUnknownErrorException extends RuntimeException {}
 
-    public class CoreCouldNotEditException extends RuntimeException {}
+    public static class CoreCouldNotEditException extends RuntimeException {}
 
-    public class CoreCouldNotSaveException extends RuntimeException {}
+    public static class CoreCouldNotSaveException extends RuntimeException {}
 
 }
diff --git a/app/src/main/java/at/tomtasche/reader/background/OdfLoader.java b/app/src/main/java/at/tomtasche/reader/background/OdfLoader.java
index e3c931dd2a17..7746957ea3ba 100644
--- a/app/src/main/java/at/tomtasche/reader/background/OdfLoader.java
+++ b/app/src/main/java/at/tomtasche/reader/background/OdfLoader.java
@@ -81,8 +81,12 @@ private void translate(Options options, Result result) throws Exception {
         CoreWrapper.CoreResult coreResult = lastCore.parse(coreOptions);
 
         String coreExtension = coreResult.extension;
-        // "unnamed" refers to default of Meta::typeToString
-        if (coreExtension != null && !coreExtension.equals("unnamed")) {
+        if (coreResult.exception == null && "pdf".equals(coreExtension)) {
+            // some PDFs do not cause an error in the core
+            // https://github.com/opendocument-app/OpenDocument.droid/issues/348#issuecomment-2446888981
+            throw new CoreWrapper.CoreCouldNotTranslateException();
+        } else if (!"unnamed".equals(coreExtension)) {
+            // "unnamed" refers to default of Meta::typeToString
             options.fileExtension = coreExtension;
 
             String fileType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(coreExtension);