diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 5a0b63219a..d1e7b26dc6 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -1140,11 +1140,6 @@ static void handle_deletes(void)
 	}
 }
 
-static char *anonymize_seed(void *data)
-{
-	return xstrdup(data);
-}
-
 static int parse_opt_anonymize_map(const struct option *opt,
 				   const char *arg, int unset)
 {
@@ -1166,7 +1161,8 @@ static int parse_opt_anonymize_map(const struct option *opt,
 	if (!keylen || !*value)
 		return error(_("--anonymize-map token cannot be empty"));
 
-	anonymize_str(map, anonymize_seed, arg, keylen, (void *)value);
+	add_anonymized_entry(map, memhash(arg, keylen), arg, keylen,
+			     xstrdup(value));
 
 	return 0;
 }
diff --git a/t/t9351-fast-export-anonymize.sh b/t/t9351-fast-export-anonymize.sh
index 77047e250d..156a647484 100755
--- a/t/t9351-fast-export-anonymize.sh
+++ b/t/t9351-fast-export-anonymize.sh
@@ -25,6 +25,7 @@ test_expect_success 'setup simple repo' '
 test_expect_success 'export anonymized stream' '
 	git fast-export --anonymize --all \
 		--anonymize-map=retain-me \
+		--anonymize-map=xyzzy:should-not-appear \
 		--anonymize-map=xyzzy:custom-name \
 		--anonymize-map=other \
 		>stream
@@ -41,6 +42,7 @@ test_expect_success 'stream omits path names' '
 
 test_expect_success 'stream contains user-specified names' '
 	grep retain-me stream &&
+	! grep should-not-appear stream &&
 	grep custom-name stream
 '