diff --git a/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationActivityV2.kt b/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationActivityV2.kt
index a9e5883e7b..f64738b47a 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationActivityV2.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationActivityV2.kt
@@ -1840,6 +1840,22 @@ class ConversationActivityV2 : PassphraseRequiredActionBarActivity(), InputBarDe
         val mediaPreppedListener = object : ListenableFuture.Listener<Boolean> {
 
             override fun onSuccess(result: Boolean?) {
+                if (result == null) {
+                    Log.w(TAG, "Media prepper returned a null result - bailing.")
+                    return
+                }
+
+                // If the attachment was too large or MediaConstraints.isSatisfied failed for some
+                // other reason then we reset the attachment manager & shown buttons then bail..
+                if (!result) {
+                    attachmentManager.clear()
+                    if (isShowingAttachmentOptions) { toggleAttachmentOptions() }
+                    return
+                }
+
+                // ..otherwise we can attempt to send the attachment(s).
+                // Note: The only multi-attachment message type is when sending images - all others
+                // attempt send on initial attachment selection.
                 sendAttachments(attachmentManager.buildSlideDeck().asAttachments(), null)
             }
 
diff --git a/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/utilities/AttachmentManager.java b/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/utilities/AttachmentManager.java
index 8225c9c6b4..e9a738637d 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/utilities/AttachmentManager.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/conversation/v2/utilities/AttachmentManager.java
@@ -65,6 +65,9 @@ public class AttachmentManager {
 
   private final static String TAG = AttachmentManager.class.getSimpleName();
 
+  // Max attachment size is 10MB, above which we display a warning toast rather than sending the msg
+  private final long MAX_ATTACHMENTS_FILE_SIZE_BYTES = 10 * 1024 * 1024;
+
   private final @NonNull Context                    context;
   private final @NonNull AttachmentListener         attachmentListener;
 
@@ -360,9 +363,18 @@ public class AttachmentManager {
                                           final @Nullable Slide slide,
                                           final @NonNull  MediaConstraints constraints)
   {
-   return slide == null                                          ||
-          constraints.isSatisfied(context, slide.asAttachment()) ||
-          constraints.canResize(slide.asAttachment());
+    // Null attachment? Not satisfied.
+    if (slide == null) return false;
+
+    // Attachments are excessively large? Not satisfied.
+    if (slide.asAttachment().getSize() > MAX_ATTACHMENTS_FILE_SIZE_BYTES) {
+      Toast.makeText(context, R.string.attachmentsErrorSize, Toast.LENGTH_SHORT).show();
+      return false;
+    }
+
+    // Otherwise our constraints-satisfied condition becomes whether we can resize it (obviously
+    // this will only work on images).
+    return constraints.canResize(slide.asAttachment());
   }
 
   public interface AttachmentListener {