diff --git a/CHANGELOG.md b/CHANGELOG.md
index 257a67d..529e961 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@
 - Fix query for organizations report [OP-3636]
 - Bump report-generation-service to most recent version
 - Write migration to harmonize date formats of change events [OP-3559]
+- datafix: cleanup of duplicate memberships [OP-3634]
 ### Deploy notes
 ```
 drc pull deltanotifier; drc up -d deltanotifier
diff --git a/config/migrations/2025/20250725120522-remove-duplicate-memberships-ocmw-municipality.sparql b/config/migrations/2025/20250725120522-remove-duplicate-memberships-ocmw-municipality.sparql
new file mode 100644
index 0000000..a55bf85
--- /dev/null
+++ b/config/migrations/2025/20250725120522-remove-duplicate-memberships-ocmw-municipality.sparql
@@ -0,0 +1,33 @@
+PREFIX org: <http://www.w3.org/ns/org#>
+PREFIX mu: <http://mu.semte.ch/vocabularies/core/>
+
+DELETE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?duplicateMembership ?p ?o .
+  }
+} WHERE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?duplicateMembership a org:Membership ;
+      org:organization ?orgB ; # OCMW
+      org:member ?orgA ; # Municipality
+      org:role <http://data.lblod.info/id/rollen/4ec7d5c39bdc4e84b4174379b9e22ad8> ;
+      ?p ?o .
+
+    # Find the other memberships with swapped organizations
+    ?correctMembership a org:Membership ;
+      org:organization ?orgA ; # Municipality
+      org:member ?orgB ; # OCMW
+      org:role <http://data.lblod.info/id/rollen/4ec7d5c39bdc4e84b4174379b9e22ad8> .
+  }
+
+  GRAPH ?gA {
+    ?orgA org:classification ?classA .
+  }
+
+  GRAPH ?gB {
+    ?orgB org:classification ?classB .
+  }
+
+  FILTER(?classA = <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/5ab0e9b8a3b2ca7c5e000001>)
+  FILTER(?classB = <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/5ab0e9b8a3b2ca7c5e000002>)
+}