diff --git a/commons/src/main/java/org/wikimedia/commons/modifications/CategoryModifier.java b/commons/src/main/java/org/wikimedia/commons/modifications/CategoryModifier.java
index 00838ade3..7e5d9f907 100644
--- a/commons/src/main/java/org/wikimedia/commons/modifications/CategoryModifier.java
+++ b/commons/src/main/java/org/wikimedia/commons/modifications/CategoryModifier.java
@@ -46,4 +46,9 @@ public class CategoryModifier extends PageModifier {
         }
         return pageContents + categoriesString.toString();
     }
+
+    @Override
+    public String getEditSumary() {
+        return String.format("Added " + params.optJSONArray(PARAM_CATEGORIES).length() + " categories.");
+    }
 }
diff --git a/commons/src/main/java/org/wikimedia/commons/modifications/ModificationsSyncAdapter.java b/commons/src/main/java/org/wikimedia/commons/modifications/ModificationsSyncAdapter.java
index 6be356026..53dedce8e 100644
--- a/commons/src/main/java/org/wikimedia/commons/modifications/ModificationsSyncAdapter.java
+++ b/commons/src/main/java/org/wikimedia/commons/modifications/ModificationsSyncAdapter.java
@@ -110,6 +110,7 @@ public class ModificationsSyncAdapter extends AbstractThreadedSyncAdapter {
                                 .param("title", contrib.getFilename())
                                 .param("token", editToken)
                                 .param("text", processedPageContent)
+                                .param("summary", sequence.getEditSummary())
                                 .post();
                     } catch (IOException e) {
                         throw new RuntimeException(e);
diff --git a/commons/src/main/java/org/wikimedia/commons/modifications/ModifierSequence.java b/commons/src/main/java/org/wikimedia/commons/modifications/ModifierSequence.java
index c58330185..c84a193d0 100644
--- a/commons/src/main/java/org/wikimedia/commons/modifications/ModifierSequence.java
+++ b/commons/src/main/java/org/wikimedia/commons/modifications/ModifierSequence.java
@@ -50,6 +50,15 @@ public class ModifierSequence {
         return pageContents;
     }
 
+    public String getEditSummary() {
+        StringBuffer editSummary = new StringBuffer();
+        for(PageModifier modifier: modifiers) {
+            editSummary.append(modifier.getEditSumary()).append(" ");
+        }
+        editSummary.append("Via Commons Mobile App");
+        return editSummary.toString();
+    }
+
     public JSONObject toJSON() {
         JSONObject data = new JSONObject();
         try {
diff --git a/commons/src/main/java/org/wikimedia/commons/modifications/PageModifier.java b/commons/src/main/java/org/wikimedia/commons/modifications/PageModifier.java
index fe09307a9..803942e17 100644
--- a/commons/src/main/java/org/wikimedia/commons/modifications/PageModifier.java
+++ b/commons/src/main/java/org/wikimedia/commons/modifications/PageModifier.java
@@ -24,6 +24,8 @@ public abstract class PageModifier {
 
     public abstract String doModification(String pageName, String pageContents);
 
+    public abstract String getEditSumary();
+
     public JSONObject toJSON() {
         JSONObject data = new JSONObject();
         try {