diff --git a/pycodestyle.py b/pycodestyle.py
index 6d3b554c..b7e0b2fb 100755
--- a/pycodestyle.py
+++ b/pycodestyle.py
@@ -860,6 +860,10 @@ def missing_whitespace_around_operator(logical_line, tokens):
                 # Tolerate the "<>" operator, even if running Python 3
                 # Deal with Python 3's annotated return value "->"
                 pass
+            elif prev_text == '/' and text == ',':
+                # Tolerate the "/" operator in function definition
+                # For more info see PEP570
+                pass
             else:
                 if need_space is True or need_space[1]:
                     # A needed trailing space was not found
diff --git a/testsuite/python38.py b/testsuite/python38.py
index 59addad4..5f62a3f1 100644
--- a/testsuite/python38.py
+++ b/testsuite/python38.py
@@ -1,4 +1,7 @@
 #: Okay
+def f(a, /, b):
+    pass
+#: Okay
 if x := 1:
     print(x)
 if m and (token := m.group(1)):