diff --git a/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMessage.java b/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMessage.java
index aa03f268d..e2ceec3b2 100644
--- a/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMessage.java
+++ b/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMessage.java
@@ -430,7 +430,7 @@ public class MimeMessage extends Message {
 
     @Override
     public InputStream getInputStream() throws MessagingException {
-        return null;
+        throw new UnsupportedOperationException();
     }
 
     @Override
diff --git a/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMultipart.java b/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMultipart.java
index 1a3637b90..22a7ff98a 100644
--- a/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMultipart.java
+++ b/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MimeMultipart.java
@@ -106,6 +106,6 @@ public class MimeMultipart extends Multipart {
 
     @Override
     public InputStream getInputStream() throws MessagingException {
-        return null;
+        throw new UnsupportedOperationException();
     }
 }