diff --git a/README.md b/README.md
index 16d95be8..1bb4d501 100644
--- a/README.md
+++ b/README.md
@@ -102,7 +102,7 @@ To this end, this provider supports the following extra specs schema:
     "properties": {
         "subnet_id": {
             "type": "string",
-            "pattern": "^subnet-[0-9a-fA-F]{17}$"
+            "pattern": "^subnet-(?:[0-9a-fA-F]{8}|[0-9a-fA-F]{17})$"
         },
         "ssh_key_name": {
             "type": "string",
diff --git a/internal/spec/spec.go b/internal/spec/spec.go
index 05fac38d..972d49a3 100644
--- a/internal/spec/spec.go
+++ b/internal/spec/spec.go
@@ -74,9 +74,9 @@ func newExtraSpecsFromBootstrapData(data params.BootstrapInstance) (*extraSpecs,
 }
 
 type extraSpecs struct {
-	SubnetID           *string          `json:"subnet_id,omitempty" jsonschema:"pattern=^subnet-[0-9a-fA-F]{17}$,description=The ID of the subnet formatted as subnet-xxxxxxxxxxxxxxxxx."`
+	SubnetID           *string          `json:"subnet_id,omitempty" jsonschema:"pattern=^subnet-(?:[0-9a-fA-F]{8}|[0-9a-fA-F]{17})$,description=The ID of the subnet formatted as subnet-xxxxxxxxxxxxxxxxx."`
 	SSHKeyName         *string          `json:"ssh_key_name,omitempty" jsonschema:"description=The name of the Key Pair to use for the instance."`
-	IAMInstanceProfile *string          `json:"iam_instance_profile,omitempty jsonschema:"description=The IAM instance profile to associate with the instance."`
+	IAMInstanceProfile *string          `json:"iam_instance_profile,omitempty" jsonschema:"description=The IAM instance profile to associate with the instance."`
 	Iops               *int32           `json:"iops,omitempty" jsonschema:"description=Specifies the number of IOPS (Input/Output Operations Per Second) provisioned for the volume. Required for io1 and io2 volumes. Optional for gp3 volumes."`
 	Throughput         *int32           `json:"throughput,omitempty" jsonschema:"description=Specifies the throughput (MiB/s) provisioned for the volume. Valid only for gp3 volumes.,minimum=125,maximum=1000"`
 	VolumeSize         *int32           `json:"volume_size,omitempty" jsonschema:"description=Specifies the size of the volume in GiB. Required unless a snapshot ID is provided."`
diff --git a/internal/spec/spec_test.go b/internal/spec/spec_test.go
index 79e099f3..7dcbbd0c 100644
--- a/internal/spec/spec_test.go
+++ b/internal/spec/spec_test.go
@@ -70,6 +70,16 @@ func TestExtraSpecsFromBootstrapData(t *testing.T) {
 			},
 			errString: "",
 		},
+		{
+			name: "specs just with older version of subnet_id",
+			input: params.BootstrapInstance{
+				ExtraSpecs: json.RawMessage(`{"subnet_id": "subnet-12345678"}`),
+			},
+			expectedOutput: &extraSpecs{
+				SubnetID: aws.String("subnet-12345678"),
+			},
+			errString: "",
+		},
 		{
 			name: "specs just with ssh_key_name",
 			input: params.BootstrapInstance{
@@ -171,7 +181,7 @@ func TestExtraSpecsFromBootstrapData(t *testing.T) {
 				ExtraSpecs: json.RawMessage(`{"subnet_id": "subnet-1"}`),
 			},
 			expectedOutput: nil,
-			errString:      "subnet_id: Does not match pattern '^subnet-[0-9a-fA-F]{17}$'",
+			errString:      "subnet_id: Does not match pattern '^subnet-(?:[0-9a-fA-F]{8}|[0-9a-fA-F]{17})$'",
 		},
 		{
 			name: "invalid type for subnet_id",