diff --git a/builtin/providers/aws/structure.go b/builtin/providers/aws/structure.go
index 1c01f89f6454..2f22d6e3a9e9 100644
--- a/builtin/providers/aws/structure.go
+++ b/builtin/providers/aws/structure.go
@@ -93,9 +93,8 @@ func expandIPPerms(
 
 		if raw, ok := m["cidr_blocks"]; ok {
 			list := raw.([]interface{})
-			perm.IPRanges = make([]*ec2.IPRange, len(list))
-			for i, v := range list {
-				perm.IPRanges[i] = &ec2.IPRange{CIDRIP: aws.String(v.(string))}
+			for _, v := range list {
+				perm.IPRanges = append(perm.IPRanges, &ec2.IPRange{CIDRIP: aws.String(v.(string))})
 			}
 		}