diff --git a/internal/httpapi/routes_crud.go b/internal/httpapi/routes_crud.go
index f818c5b..de38fd4 100644
--- a/internal/httpapi/routes_crud.go
+++ b/internal/httpapi/routes_crud.go
@@ -105,11 +105,39 @@ func (s *Server) handlePatchModule(w http.ResponseWriter, r *http.Request) {
 	if !ok || !s.requireAtLeast(w, a, "editor") {
 		return
 	}
+	rawBody, err := io.ReadAll(r.Body)
+	if err != nil {
+		writeProblem(w, http.StatusBadRequest, "Bad Request", "invalid body")
+		return
+	}
 	var body store.ModulePatch
-	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+	if err := json.Unmarshal(rawBody, &body); err != nil {
 		writeProblem(w, http.StatusBadRequest, "Bad Request", "invalid json")
 		return
 	}
+	// NOTE:
+	// In Go, unmarshalling JSON `null` into pointer fields results in nil,
+	// which is indistinguishable from "field omitted". For PATCH we need to
+	// distinguish these cases so clients can explicitly clear nullable fields.
+	var raw map[string]json.RawMessage
+	if err := json.Unmarshal(rawBody, &raw); err == nil {
+		if v, ok := raw["default_community_id"]; ok && string(v) == "null" {
+			empty := ""
+			body.DefaultCommunityID = &empty
+		}
+		if v, ok := raw["doh_profile_id"]; ok && string(v) == "null" {
+			empty := ""
+			body.DohProfileID = &empty
+		}
+		if v, ok := raw["cron_expr"]; ok && string(v) == "null" {
+			empty := ""
+			body.CronExpr = &empty
+		}
+		if v, ok := raw["refresh_interval_sec"]; ok && string(v) == "null" {
+			zero := 0
+			body.RefreshIntervalSec = &zero
+		}
+	}
 	mod, err := s.store.UpdateModule(a.TenantID, r.PathValue("module_id"), &body)
 	if err != nil {
 		writeStoreErr(w, err)