diff --git a/configure.ac b/configure.ac
index 663dc32fd28c4..2673780b22601 100644
--- a/configure.ac
+++ b/configure.ac
@@ -148,7 +148,7 @@ PHP_RUNPATH_SWITCH
 
 dnl Checks for some support/generator progs.
 PHP_PROG_BISON([3.0.0])
-PHP_PROG_RE2C([1.0.3], [--no-generation-date])
+PHP_PROG_RE2C([1.0.3], [--no-generation-date -W])
 dnl Find installed PHP. Minimum supported version for gen_stub.php is PHP 7.4.
 PHP_PROG_PHP([7.4])
 
diff --git a/scripts/dev/genfiles b/scripts/dev/genfiles
index 124a10de34581..b8d35cff6bf6c 100755
--- a/scripts/dev/genfiles
+++ b/scripts/dev/genfiles
@@ -37,7 +37,7 @@ YACC=${YACC:-bison}
 YACC="$YACC -l"
 YFLAGS="-Wall"
 RE2C=${RE2C:-re2c}
-RE2C_FLAGS="--no-generation-date -i"
+RE2C_FLAGS="--no-generation-date -i -W"
 SED=${SED:-sed}
 MAKE=${MAKE:-make}
 
diff --git a/win32/build/confutils.js b/win32/build/confutils.js
index 0f97a1a2d29c6..d6d560fa43d9c 100644
--- a/win32/build/confutils.js
+++ b/win32/build/confutils.js
@@ -3017,7 +3017,7 @@ function toolset_setup_project_tools()
 	}
 
 	var RE2C = PATH_PROG('re2c');
-	DEFINE('RE2C_FLAGS', '--no-generation-date');
+	DEFINE('RE2C_FLAGS', '--no-generation-date -W');
 	if (RE2C) {
 		var RE2CVERS = probe_binary(RE2C, "version");
 		STDOUT.WriteLine('  Detected re2c version ' + RE2CVERS);