diff --git a/piptools/_compat/pip_compat.py b/piptools/_compat/pip_compat.py
index 4405cc6d..d956ab24 100644
--- a/piptools/_compat/pip_compat.py
+++ b/piptools/_compat/pip_compat.py
@@ -23,7 +23,7 @@
 if TYPE_CHECKING:
     from pip._internal.metadata.importlib import Distribution as _ImportLibDist
 
-from ..utils import PIP_VERSION, canonicalize_ireq
+from ..utils import PIP_VERSION, copy_install_requirement
 
 
 @dataclass(frozen=True)
@@ -89,8 +89,7 @@ def parse_requirements(
             file_link = FileLink(install_req.link.url)
             file_link._url = parsed_req.requirement
             install_req.link = file_link
-        canonicalize_ireq(install_req)
-        yield install_req
+        yield copy_install_requirement(install_req)
 
 
 def create_wheel_cache(cache_dir: str, format_control: str | None = None) -> WheelCache:
diff --git a/piptools/build.py b/piptools/build.py
index 88fc0085..c19e206b 100644
--- a/piptools/build.py
+++ b/piptools/build.py
@@ -17,7 +17,7 @@
 from pip._vendor.packaging.markers import Marker
 from pip._vendor.packaging.requirements import Requirement
 
-from .utils import canonicalize_ireq, install_req_from_line
+from .utils import copy_install_requirement, install_req_from_line
 
 if sys.version_info >= (3, 11):
     import tomllib
@@ -231,7 +231,7 @@ def _prepare_requirements(
             replaced_package_name = req.replace(package_name, str(package_dir), 1)
             parts = parse_req_from_line(replaced_package_name, comes_from)
 
-        yield canonicalize_ireq(
+        yield copy_install_requirement(
             InstallRequirement(
                 parts.requirement,
                 comes_from,
diff --git a/piptools/utils.py b/piptools/utils.py
index 80a2abda..8d04f7a7 100644
--- a/piptools/utils.py
+++ b/piptools/utils.py
@@ -93,20 +93,8 @@ def comment(text: str) -> str:
     return click.style(text, fg="green")
 
 
-def canonicalize_ireq(ireq: InstallRequirement) -> InstallRequirement:
-    """
-    Return a copy of ireq with canonicalized extras strings
-    """
-    ireq = copy_install_requirement(
-        ireq, extras=set(map(canonicalize_name, ireq.extras))
-    )
-    if ireq.req:
-        ireq.req.extras = set(ireq.extras)
-    return ireq
-
-
 def install_req_from_line(*args: Any, **kwargs: Any) -> InstallRequirement:
-    return canonicalize_ireq(_install_req_from_line(*args, **kwargs))
+    return copy_install_requirement(_install_req_from_line(*args, **kwargs))
 
 
 def make_install_requirement(
@@ -536,6 +524,10 @@ def copy_install_requirement(
     if "req" not in kwargs:
         kwargs["req"] = copy.deepcopy(template.req)
 
+    kwargs["extras"] = set(map(canonicalize_name, kwargs["extras"]))
+    if kwargs["req"]:
+        kwargs["req"].extras = set(kwargs["extras"])
+
     ireq = InstallRequirement(**kwargs)
 
     # If the original_link was None, keep it so. Passing `link` as an