diff --git a/pkg/sql/colexec/agg/avg/avg.go b/pkg/sql/colexec/agg/avg/avg.go
index ddc68cd219149b805416e088be868551e50553e0..2d81328fadaf285d44a5c57f0fff9febbac74ba8 100644
--- a/pkg/sql/colexec/agg/avg/avg.go
+++ b/pkg/sql/colexec/agg/avg/avg.go
@@ -126,7 +126,7 @@ func (a *Decimal64Avg) BatchFill(rs, vs any, start, count int64, vps []uint64, z
 			continue
 		}
 		j := vps[i] - 1
-		a.cnts[j] += zs[j]
+		a.cnts[j] += zs[i+start]
 	}
 	return nil
 }
@@ -180,7 +180,7 @@ func (a *Decimal128Avg) BatchFill(rs, vs any, start, count int64, vps []uint64,
 			continue
 		}
 		j := vps[i] - 1
-		a.cnts[j] += zs[j]
+		a.cnts[j] += zs[i+start]
 	}
 	return nil
 }