diff --git a/amalgamate.py b/amalgamate.py
index 1916bb0..2102f30 100644
--- a/amalgamate.py
+++ b/amalgamate.py
@@ -67,6 +67,7 @@
     header.add_text("/// to prevent private header inclusion.")
     header.add_text("#define JSON_IS_AMALGAMATION")
     header.add_file("include/json/version.h")
+    header.add_file("include/json/allocator.h")
     header.add_file("include/json/config.h")
     header.add_file("include/json/forwards.h")
     header.add_file("include/json/features.h")