diff --git a/setup.py b/setup.py
index 09202a658c..7861619410 100755
--- a/setup.py
+++ b/setup.py
@@ -13,12 +13,14 @@
 
 NAME: str = dist.get_name()  # type: ignore
 
-# Check if building for Pyodide
-is_pyodide = os.getenv("PYODIDE", "0") == "1"
-
-if is_pyodide:
-    # For pyodide we build a universal wheel that must be pure-python
-    # so we must omit the cython-version of scan.
+# Build without optional compiled extensions. Keep PYODIDE as a compatibility
+# alias for existing downstream builds.
+is_pure_python = (
+    os.getenv("PYTENSOR_PURE_PYTHON", "0") == "1" or os.getenv("PYODIDE", "0") == "1"
+)
+
+if is_pure_python:
+    # Omit the optional Cython implementation of scan.
     ext_modules = []
 else:
     ext_modules = [