diff --git a/rest/src/main/groovy/whelk/rest/api/SearchUtils.groovy b/rest/src/main/groovy/whelk/rest/api/SearchUtils.groovy
index a6a9395b2a..9118b604a7 100644
--- a/rest/src/main/groovy/whelk/rest/api/SearchUtils.groovy
+++ b/rest/src/main/groovy/whelk/rest/api/SearchUtils.groovy
@@ -383,6 +383,7 @@ class SearchUtils {
             aggregation['buckets'].each { bucket ->
                 String itemId = bucket['key']
 
+                Map observation
                 if (key in multiSelected.keySet()) {
                     String param = makeParam(key, itemId)
                     boolean isSelected = escapeQueryParam(itemId) in multiSelected[key]
@@ -390,22 +391,28 @@ class SearchUtils {
                         ? baseUrlForKey.replace("&${param}", '') // FIXME: generate up-link in a cleaner way
                         : "${baseUrlForKey}&${param}"
 
-                    Map observation = ['totalItems': bucket.getAt('doc_count'),
+                    observation = ['totalItems': bucket.getAt('doc_count'),
                                        'view': [(JsonLd.ID_KEY): searchPageUrl],
                                        '_selected': isSelected,
                                        'object': lookup.chip(itemId)]
-
-                    observations << observation
                 }
                 else {
                     String searchPageUrl = "${baseUrlForKey}&${ESQuery.AND_PREFIX}${makeParam(key, itemId)}"
 
-                    Map observation = ['totalItems': bucket.getAt('doc_count'),
+                    observation = ['totalItems': bucket.getAt('doc_count'),
                                        'view': [(JsonLd.ID_KEY): searchPageUrl],
                                        'object': lookup.chip(itemId)]
 
-                    observations << observation
                 }
+
+                Map bucketAggs = bucket[ESQuery.FILTERED_AGG_NAME]
+                if (bucketAggs) {
+                  Map nestedAggs = bucketAggs.clone()
+                  nestedAggs.remove('doc_count')
+                  observation = addSlices(lookup, observation, nestedAggs, baseUrlForKey, null, multiSelected)
+                }
+
+                observations << observation
             }
 
             if (observations) {
diff --git a/whelk-core/src/main/groovy/whelk/search/ESQuery.groovy b/whelk-core/src/main/groovy/whelk/search/ESQuery.groovy
index 43dcefe7cf..9bf163ca0f 100644
--- a/whelk-core/src/main/groovy/whelk/search/ESQuery.groovy
+++ b/whelk-core/src/main/groovy/whelk/search/ESQuery.groovy
@@ -948,16 +948,20 @@ class ESQuery {
         }
 
         keys.each { key ->
-            String sort = tree[key]?.sort =='key' ? '_key' : '_count'
-            def sortOrder = tree[key]?.sortOrder =='asc' ? 'asc' : 'desc'
+            Map treeNode = tree[key]
+            String sort = treeNode?.sort =='key' ? '_key' : '_count'
+            def sortOrder = treeNode?.sortOrder =='asc' ? 'asc' : 'desc'
             String termPath = getInferredTermPath(key)
 
             // Core agg query
-            query[termPath] = ['terms': [
+            def coreQuery = [
+                'terms': [
                     'field': termPath,
-                    'size' : tree[key]?.size ?: size,
-                    'order': [(sort): sortOrder]]
+                    'size' : treeNode?.size ?: size,
+                    'order': [(sort): sortOrder]
+                ]
             ]
+            query[termPath] = coreQuery
 
             // If field is nested, wrap agg query with nested
             nestedFields.find{ key.startsWith(it) }?.with { nestedField ->
@@ -974,8 +978,23 @@ class ESQuery {
                 'filter': ['bool': ['must': filters]]
             ]
 
-            if (tree[key].subItems instanceof Map) {
-                query[termPath]['aggs'] = buildAggQuery(tree[key].subItems, multiSelectFilters, size)
+            if (treeNode.subItems instanceof Map) {
+                def subAggQuery = buildAggQuery(treeNode.subItems, multiSelectFilters, size)
+                // TODO: factor out parts of buildAggQuery to avoid this reshuffle.
+                //coreQuery['aggs'] = subAggQuery
+                // TODO: handle multiple keys.
+                def iter = subAggQuery.iterator()
+                if (iter.hasNext()) {
+                    def entry = iter.next()
+                    def subkey = entry.getKey()
+                    def subvalue = entry.getValue()
+                    coreQuery['aggs'] = [
+                        (FILTERED_AGG_NAME): [
+                            'aggs': [ (subkey): subvalue['aggs'][FILTERED_AGG_NAME] ],
+                            'filter': subvalue['filter']
+                        ]
+                    ]
+                }
             }
         }
         return query