diff --git a/CHANGELOG.md b/CHANGELOG.md
index 62fd6c6..c8c35e6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,9 @@
 
 - Upgraded buildx from 0.16.0 to 0.18.0.
 
+### Fixed
+- Custom `# syntax=` directives no longer cause validation errors. (https://github.com/pulumi/pulumi-docker-build/issues/300)
+
 ## 0.0.7 (2024-10-16)
 
 ### Fixed
diff --git a/provider/internal/dockerfile.go b/provider/internal/dockerfile.go
index 1757dbf..4d17a6c 100644
--- a/provider/internal/dockerfile.go
+++ b/provider/internal/dockerfile.go
@@ -15,6 +15,7 @@
 package internal
 
 import (
+	"bytes"
 	"errors"
 	"io"
 	"os"
@@ -96,13 +97,26 @@ func (d *Dockerfile) validate(preview bool, c *Context) error {
 }
 
 func parseDockerfile(r io.Reader) error {
-	parsed, err := parser.Parse(r)
+	df, _ := io.ReadAll(r)
+	syntax, _, _, _ := parser.DetectSyntax(df)
+	if syntax == "" {
+		syntax = os.Getenv("BUILDKIT_SYNTAX")
+	}
+
+	// Disable validation if this uses a custom syntax.
+	if syntax != "" && syntax != "docker/dockerfile:1" {
+		return nil
+	}
+
+	parsed, err := parser.Parse(bytes.NewReader(df))
 	if err != nil {
 		return newCheckFailure(err, "dockerfile")
 	}
+
 	_, _, err = instructions.Parse(parsed.AST, nil)
 	if err != nil {
-		return err
+		return newCheckFailure(err, "dockerfile")
 	}
+
 	return nil
 }
diff --git a/provider/internal/dockerfile_test.go b/provider/internal/dockerfile_test.go
index bd9fc74..2572d59 100644
--- a/provider/internal/dockerfile_test.go
+++ b/provider/internal/dockerfile_test.go
@@ -57,12 +57,31 @@ func TestValidateDockerfile(t *testing.T) {
 			},
 			wantErr: "unknown instruction: RUNN",
 		},
+		{
+			name: "invalid syntax inline with default syntax directive",
+			d: Dockerfile{
+				Inline: `# syntax=docker/dockerfile:1
+				RUNN it`,
+			},
+			wantErr: "unknown instruction: RUNN",
+		},
 		{
 			name: "valid syntax inline",
 			d: Dockerfile{
 				Inline: "FROM scratch",
 			},
 		},
+		{
+			name: "valid custom syntax inline",
+			d: Dockerfile{
+				Inline: `# syntax=docker.io/docker/dockerfile:1.7-labs
+FROM public.ecr.aws/docker/library/node:22-alpine AS base
+
+WORKDIR /app
+COPY --parents ./package.json ./package-lock.json ./apps/*/package.json ./packages/*/package.json ./
+`,
+			},
+		},
 		{
 			name:    "unset",
 			d:       Dockerfile{},