diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -783,7 +783,7 @@
         with self.assertRaises(csv.Error) as cm:
             mydialect()
         self.assertEqual(str(cm.exception),
-                         '"quotechar" must be an 1-character string')
+                         '"quotechar" must be a 1-character string')
 
         mydialect.quotechar = 4
         with self.assertRaises(csv.Error) as cm:
@@ -806,13 +806,13 @@
         with self.assertRaises(csv.Error) as cm:
             mydialect()
         self.assertEqual(str(cm.exception),
-                         '"delimiter" must be an 1-character string')
+                         '"delimiter" must be a 1-character string')
 
         mydialect.delimiter = ""
         with self.assertRaises(csv.Error) as cm:
             mydialect()
         self.assertEqual(str(cm.exception),
-                         '"delimiter" must be an 1-character string')
+                         '"delimiter" must be a 1-character string')
 
         mydialect.delimiter = b","
         with self.assertRaises(csv.Error) as cm:
diff --git a/Modules/_csv.c b/Modules/_csv.c
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -248,7 +248,7 @@
             len = PyUnicode_GetLength(src);
             if (len > 1) {
                 PyErr_Format(PyExc_TypeError,
-                    "\"%s\" must be an 1-character string",
+                    "\"%s\" must be a 1-character string",
                     name);
                 return -1;
             }
@@ -432,7 +432,7 @@
         goto err;
     if (self->delimiter == 0) {
         PyErr_SetString(PyExc_TypeError,
-                        "\"delimiter\" must be an 1-character string");
+                        "\"delimiter\" must be a 1-character string");
         goto err;
     }
     if (quotechar == Py_None && quoting == NULL)