diff --git a/google_keymaster_test.cpp b/google_keymaster_test.cpp
index 81c4f8b..a492743 100644
--- a/google_keymaster_test.cpp
+++ b/google_keymaster_test.cpp
@@ -438,8 +438,8 @@
     const keymaster_key_blob_t& key_blob() { return generate_response_.key_blob; }
 
     const keymaster_key_blob_t& corrupt_key_blob() {
-        ++generate_response_.key_blob
-              .key_material[generate_response_.key_blob.key_material_size / 2];
+        uint8_t* tmp = const_cast<uint8_t*>(generate_response_.key_blob.key_material);
+        ++tmp[generate_response_.key_blob.key_material_size / 2];
         return generate_response_.key_blob;
     }
 
diff --git a/include/keymaster/keymaster_defs.h b/include/keymaster/keymaster_defs.h
index ab0676f..c35f48b 100644
--- a/include/keymaster/keymaster_defs.h
+++ b/include/keymaster/keymaster_defs.h
@@ -293,7 +293,7 @@
 } keymaster_key_characteristics_t;
 
 typedef struct {
-    uint8_t* key_material;
+    const uint8_t* key_material;
     size_t key_material_size;
 } keymaster_key_blob_t;