diff --git a/grails-app/services/au/org/ala/ecodata/ProjectService.groovy b/grails-app/services/au/org/ala/ecodata/ProjectService.groovy
index 41b8b09a0..8e6840a47 100644
--- a/grails-app/services/au/org/ala/ecodata/ProjectService.groovy
+++ b/grails-app/services/au/org/ala/ecodata/ProjectService.groovy
@@ -485,6 +485,11 @@ class ProjectService {
                 props = includeProjectActivities(props, projectActivities)
 
                 try {
+                    // Custom currently holds keys "details" and "dataSets".  Only update the "custom" properties
+                    // that are supplied in the update, leaving the others intact.
+                    if (project.custom && props.custom) {
+                        project.custom.putAll(props.remove('custom'))
+                    }
                     bindEmbeddedProperties(project, props)
                     commonService.updateProperties(project, props)
                     if (shouldUpdateCollectory) {
diff --git a/src/test/groovy/au/org/ala/ecodata/ProjectServiceSpec.groovy b/src/test/groovy/au/org/ala/ecodata/ProjectServiceSpec.groovy
index 856ee7b16..a5b01f8e7 100644
--- a/src/test/groovy/au/org/ala/ecodata/ProjectServiceSpec.groovy
+++ b/src/test/groovy/au/org/ala/ecodata/ProjectServiceSpec.groovy
@@ -828,4 +828,26 @@ class ProjectServiceSpec extends MongoSpec implements ServiceUnitTest<ProjectSer
 
     }
 
+    void "The update method merges the Project custom property"() {
+        setup:
+        Map dataSet = [name: 'Test Data Set', description: 'Test Description', dataSetId:'d1']
+        Project project = new Project(projectId: '345', name: "Project 345", isMERIT: true, hubId:"12345", custom:[dataSets:[dataSet], details:[name:'name']])
+        project.save(flush: true, failOnError: true)
+
+
+        when:
+        Map resp = service.update([custom:[details:[name:'name 2']]], project.projectId, false)
+
+        then:
+        resp.status == 'ok'
+        Project actual = Project.findByProjectId(project.projectId)
+        actual.projectId == project.projectId
+        actual.name == project.name
+        actual.isMERIT == project.isMERIT
+        actual.hubId == project.hubId
+        actual.custom.dataSets == project.custom.dataSets
+        actual.custom.details == [name:'name 2']
+
+    }
+
 }