diff --git a/configure.ac b/configure.ac
index c9bf5317c..875de7f5d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -824,22 +824,22 @@ AC_CHECK_TYPES([__int128_t])
 AC_CHECK_TYPES([__uint128_t])
 AC_CHECK_TYPES([long double])
 
-AC_CHECK_SIZEOF(char)
-AC_CHECK_SIZEOF(char8_t)
-AC_CHECK_SIZEOF(char16_t)
-AC_CHECK_SIZEOF(char32_t)
-AC_CHECK_SIZEOF(short)
-AC_CHECK_SIZEOF(int)
-AC_CHECK_SIZEOF(long)
-AC_CHECK_SIZEOF(long long)
-AC_CHECK_SIZEOF(float)
-AC_CHECK_SIZEOF(double)
-AC_CHECK_SIZEOF(long double)
-AC_CHECK_SIZEOF(int128_t)
-AC_CHECK_SIZEOF(uint128_t)
-AC_CHECK_SIZEOF(__int128)
-AC_CHECK_SIZEOF(__int128_t)
-AC_CHECK_SIZEOF(__uint128_t)
+AC_CHECK_SIZEOF([char])
+AC_CHECK_SIZEOF([char8_t])
+AC_CHECK_SIZEOF([char16_t])
+AC_CHECK_SIZEOF([char32_t])
+AC_CHECK_SIZEOF([short])
+AC_CHECK_SIZEOF([int])
+AC_CHECK_SIZEOF([long])
+AC_CHECK_SIZEOF([long long])
+AC_CHECK_SIZEOF([float])
+AC_CHECK_SIZEOF([double])
+AC_CHECK_SIZEOF([long double])
+AC_CHECK_SIZEOF([int128_t])
+AC_CHECK_SIZEOF([uint128_t])
+AC_CHECK_SIZEOF([__int128])
+AC_CHECK_SIZEOF([__int128_t])
+AC_CHECK_SIZEOF([__uint128_t])
 
 dnl -fsigned-char ensures 'char' is signed on all platforms
 RB_VAR_PREPEND([CFLAGS], ["-fsigned-char"])