diff --git a/test/net/addr/ip.cpp b/test/net/addr/ip.cpp
index 2ce2580..5fef26a 100644
--- a/test/net/addr/ip.cpp
+++ b/test/net/addr/ip.cpp
@@ -3,6 +3,7 @@
 #include <stdplus/net/addr/ip.hpp>
 #include <stdplus/numeric/endian.hpp>
 
+#include <format>
 #include <string_view>
 
 #include <gtest/gtest.h>
@@ -48,6 +49,7 @@
     EXPECT_EQ("1.15.3.4", tsh(In4Addr{1, 15, 3, 4}));
     EXPECT_EQ("0.0.0.0", tsh(In4Addr{}));
     EXPECT_EQ("a 1.15.3.4 b", fmt::format("a {} b", In4Addr{1, 15, 3, 4}));
+    EXPECT_EQ("a 1.15.3.4 b", std::format("a {} b", In4Addr{1, 15, 3, 4}));
 }
 
 TEST(EqualOperator, In6Addr)
@@ -157,6 +159,7 @@
                                                 0xff, 0xff, 192, 168, 0, 1}));
 
     EXPECT_EQ("a ff00:: b", fmt::format("a {} b", In6Addr{0xff}));
+    EXPECT_EQ("a ff00:: b", std::format("a {} b", In6Addr{0xff}));
 }
 
 TEST(EqualOperator, InAnyAddr)
@@ -221,6 +224,7 @@
     EXPECT_EQ("ff::", tsh(In6Addr{0, 0xff}));
 
     EXPECT_EQ("a ff00:: b", fmt::format("a {} b", InAnyAddr{In6Addr{0xff}}));
+    EXPECT_EQ("a ff00:: b", std::format("a {} b", InAnyAddr{In6Addr{0xff}}));
     EXPECT_NE("0.0.0.0"_ip, std::optional<InAnyAddr>());
     EXPECT_EQ("0.0.0.0"_ip, std::optional<InAnyAddr>(In4Addr{}));
 }