diff --git a/src/pip/_internal/operations/check.py b/src/pip/_internal/operations/check.py
index 184676550c7..e904309c90c 100644
--- a/src/pip/_internal/operations/check.py
+++ b/src/pip/_internal/operations/check.py
@@ -62,9 +62,7 @@ def check_package_set(package_set, should_ignore=None):
     package name and returns a boolean.
     """
     if should_ignore:
-        should_ignore_package = should_ignore
-    else:
-        def should_ignore_package(name):
+        def should_ignore(name):
             # type: (str) -> bool
             return False
 
@@ -76,7 +74,7 @@ def should_ignore_package(name):
         missing_deps = set()  # type: Set[Missing]
         conflicting_deps = set()  # type: Set[Conflicting]
 
-        if should_ignore_package(package_name):
+        if should_ignore and should_ignore(package_name):
             continue
 
         for req in package_set[package_name].requires: