diff --git a/build.py b/build.py
index 772e0cb..766bc3c 100644
--- a/build.py
+++ b/build.py
@@ -10,17 +10,14 @@ def build(setup_kwargs):
     print(f"Contents of current directory: {os.listdir('.')}")
     print(f"Contents of iscc_core directory: {os.listdir('iscc_core')}")
 
-    try:
-        from Cython.Build import cythonize
-
-        use_cython = True
-        print("Cython is available")
-    except ImportError:
-        use_cython = False
-        print("Cython is not available")
+    # Check if we're building with Cython
+    use_cython = "cython" in setup_kwargs.get("extras_require", {}).get("cython", [])
 
     if use_cython:
         try:
+            from Cython.Build import cythonize
+
+            print("Cython is available and will be used")
             ext_modules = cythonize(
                 [
                     Extension("iscc_core.cdc", ["iscc_core/cdc.py"]),
@@ -37,22 +34,18 @@ def build(setup_kwargs):
             for ext in ext_modules:
                 print(f"Extension: {ext.name}")
 
-            # Force the build process
-            setup(**setup_kwargs)
-            print("Build process completed")
-
-            # Check if the compiled modules exist
-            for ext in ext_modules:
-                module_name = ext.name.split(".")[-1]
-                compiled_file = f"{module_name}.cp{sys.version_info.major}{sys.version_info.minor}-win_amd64.pyd"
-                if os.path.exists(os.path.join("iscc_core", compiled_file)):
-                    print(f"Compiled module found: {compiled_file}")
-                else:
-                    print(f"Compiled module not found: {compiled_file}")
-        except Exception as e:
-            print(f"Failed to prepare or build Cython modules: {e}")
-            print("Falling back to pure Python")
+            # Add Cython to build requirements
+            setup_kwargs.setdefault("build_requires", []).extend(
+                ["Cython>=3", "setuptools", "wheel"]
+            )
+        except ImportError:
+            print("Cython is not available, falling back to pure Python")
+            use_cython = False
     else:
-        print("Cython not available, using pure Python")
+        print("Not building with Cython, using pure Python")
+
+    if not use_cython:
+        # Remove any Cython-related build options
+        setup_kwargs.pop("ext_modules", None)
 
     print(f"Setup kwargs: {setup_kwargs}")
diff --git a/iscc_core/__init__.py b/iscc_core/__init__.py
index 06fe58b..50abf6b 100644
--- a/iscc_core/__init__.py
+++ b/iscc_core/__init__.py
@@ -1,4 +1,3 @@
-import sys
 import os
 
 __version__ = "1.1.0"
@@ -11,10 +10,12 @@ def _using_cython_modules():  # pragma: no cover
         try:
             module_obj = __import__(f"iscc_core.{module}", fromlist=[module])
             module_path = getattr(module_obj, "__file__", "")
+            module_type = type(module_obj)
             if module_path.endswith((".so", ".pyd")):
                 cython_modules.append(module)
-            print(f"Module {module} path: {module_path}")
-            print(f"Module {module} type: {type(module_obj)}")
+            print(f"Module {module}:")
+            print(f"  Path: {module_path}")
+            print(f"  Type: {module_type}")
         except ImportError as e:
             print(f"Error importing {module}: {e}")
     print(f"Cython modules: {cython_modules}")
diff --git a/pyproject.toml b/pyproject.toml
index f61df86..10fcfc8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -99,5 +99,5 @@ generate-setup-file = true
 script = "build.py"
 
 [build-system]
-requires = ["poetry-core>=1.0.0", "Cython>=3", "setuptools", "wheel"]
+requires = ["poetry-core>=1.0.0"]
 build-backend = "poetry.core.masonry.api"