diff --git a/include/v8-isolate.h b/include/v8-isolate.h
index e9f531973b..9659300751 100644
--- a/include/v8-isolate.h
+++ b/include/v8-isolate.h
@@ -233,7 +233,7 @@ class V8_EXPORT Isolate {
      * Explicitly specify a startup snapshot blob. The embedder owns the blob.
      * The embedder *must* ensure that the snapshot is from a trusted source.
      */
-    StartupData* snapshot_blob = nullptr;
+    const StartupData* snapshot_blob = nullptr;
 
     /**
      * Enables the host application to provide a mechanism for recording
diff --git a/include/v8-snapshot.h b/include/v8-snapshot.h
index 2400357cf6..b15a2b1922 100644
--- a/include/v8-snapshot.h
+++ b/include/v8-snapshot.h
@@ -91,7 +91,7 @@ class V8_EXPORT SnapshotCreator {
    */
   SnapshotCreator(Isolate* isolate,
                   const intptr_t* external_references = nullptr,
-                  StartupData* existing_blob = nullptr);
+                  const StartupData* existing_blob = nullptr);
 
   /**
    * Create and enter an isolate, and set it up for serialization.
@@ -102,7 +102,7 @@ class V8_EXPORT SnapshotCreator {
    *        that must be equivalent to CreateParams::external_references.
    */
   SnapshotCreator(const intptr_t* external_references = nullptr,
-                  StartupData* existing_blob = nullptr);
+                  const StartupData* existing_blob = nullptr);
 
   /**
    * Destroy the snapshot creator, and exit and dispose of the Isolate
diff --git a/src/api/api.cc b/src/api/api.cc
index 09217e9730..3b53d5db76 100644
--- a/src/api/api.cc
+++ b/src/api/api.cc
@@ -546,7 +546,7 @@ struct SnapshotCreatorData {
 
 SnapshotCreator::SnapshotCreator(Isolate* v8_isolate,
                                  const intptr_t* external_references,
-                                 StartupData* existing_snapshot) {
+                                 const StartupData* existing_snapshot) {
   SnapshotCreatorData* data = new SnapshotCreatorData(v8_isolate);
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
   i_isolate->set_array_buffer_allocator(&data->allocator_);
@@ -568,7 +568,7 @@ SnapshotCreator::SnapshotCreator(Isolate* v8_isolate,
 }
 
 SnapshotCreator::SnapshotCreator(const intptr_t* external_references,
-                                 StartupData* existing_snapshot)
+                                 const StartupData* existing_snapshot)
     : SnapshotCreator(Isolate::Allocate(), external_references,
                       existing_snapshot) {}