diff --git a/test/numeric/str.cpp b/test/numeric/str.cpp
index 5646045..008cbe5 100644
--- a/test/numeric/str.cpp
+++ b/test/numeric/str.cpp
@@ -10,7 +10,7 @@
 TEST(IntToStr, Uint8_10)
 {
     IntToStr<10, uint8_t> enc;
-    static_assert(enc.buf_size == 3);
+    static_assert(enc.buf_size == 4);
     char buf[enc.buf_size];
     EXPECT_EQ("0", std::string_view(buf, enc(buf, 0)));
     EXPECT_EQ("42", std::string_view(buf, enc(buf, 42)));
@@ -22,7 +22,7 @@
 TEST(IntToStr, Int8_10)
 {
     IntToStr<10, int8_t> enc;
-    static_assert(enc.buf_size == 4);
+    static_assert(enc.buf_size == 5);
     char buf[enc.buf_size];
     EXPECT_EQ("42", std::string_view(buf, enc(buf, 42)));
     EXPECT_EQ("-127", std::string_view(buf, enc(buf, -127)));
@@ -31,7 +31,7 @@
 TEST(IntToStr, Uint16_10)
 {
     IntToStr<10, uint16_t> enc;
-    static_assert(enc.buf_size == 5);
+    static_assert(enc.buf_size == 6);
     char buf[enc.buf_size];
     EXPECT_EQ("55255", std::string_view(buf, enc(buf, 55255, 3)));
 }