diff --git a/runtime/sam/op/aggregate/aggregate.go b/runtime/sam/op/aggregate/aggregate.go
index 1af3155b9a..991e17a746 100644
--- a/runtime/sam/op/aggregate/aggregate.go
+++ b/runtime/sam/op/aggregate/aggregate.go
@@ -319,7 +319,7 @@ func (a *Aggregator) Consume(batch sbuf.Batch, this super.Value) error {
 	keyBytes := a.keyCache[:0]
 	var prim super.Value
 	for i, keyExpr := range a.keyExprs {
-		key := keyExpr.Eval(this)
+		key := keyExpr.Eval(this).SuperDeunion()
 		if key.IsQuiet() {
 			return nil
 		}
diff --git a/runtime/vam/op/aggregate/aggregate.go b/runtime/vam/op/aggregate/aggregate.go
index 97a96f0f7a..13c8be6f2c 100644
--- a/runtime/vam/op/aggregate/aggregate.go
+++ b/runtime/vam/op/aggregate/aggregate.go
@@ -85,7 +85,7 @@ func (a *Aggregate) Pull(done bool) (vector.Any, error) {
 				vals = append(vals, v)
 			}
 		}
-		vector.Apply(vector.ApplyRipUnions, func(args ...vector.Any) vector.Any {
+		vector.Apply(vector.ApplyRipUnions|vector.ApplyRipFusions, func(args ...vector.Any) vector.Any {
 			a.consume(args[:len(keys)], args[len(keys):])
 			// XXX Perhaps there should be a "consume" version of Apply where
 			// no return value is expected.
diff --git a/runtime/ztests/op/aggregate/keys.yaml b/runtime/ztests/op/aggregate/keys.yaml
new file mode 100644
index 0000000000..f815ce10c4
--- /dev/null
+++ b/runtime/ztests/op/aggregate/keys.yaml
@@ -0,0 +1,10 @@
+# Test that key values are deunioned and defused.
+spq: count() by this
+
+input: |
+  1
+  1::(int64|null)
+  fusion(1::(int64|null),<int64>)
+
+output: |
+  {that:1,count:3}