diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 5b59d393213ac..dd42e3ad916f6 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -460,11 +460,19 @@ function number_format_i18n( $number, $decimals = 0 ) {
  * @since 2.3.0
  * @since 6.0.0 Support for PB, EB, ZB, and YB was added.
  *
- * @param int|string $bytes    Number of bytes. Note max integer size for integers.
- * @param int        $decimals Optional. Precision of number of decimal places. Default 0.
+ * @param int|float|string $bytes    Number of bytes. Note max integer size for integers.
+ * @param int              $decimals Optional. Precision of number of decimal places. Default 0.
  * @return string|false Number string on success, false on failure.
+ *
+ * @phpstan-param int|float|numeric-string $bytes
  */
 function size_format( $bytes, $decimals = 0 ) {
+	if ( ! is_numeric( $bytes ) ) {
+		return false;
+	}
+
+	$bytes = (float) $bytes;
+
 	$quant = array(
 		/* translators: Unit symbol for yottabyte. */
 		_x( 'YB', 'unit symbol' ) => YB_IN_BYTES,
@@ -486,13 +494,13 @@ function size_format( $bytes, $decimals = 0 ) {
 		_x( 'B', 'unit symbol' )  => 1,
 	);
 
-	if ( 0 === $bytes ) {
+	if ( 0.0 === $bytes ) {
 		/* translators: Unit symbol for byte. */
 		return number_format_i18n( 0, $decimals ) . ' ' . _x( 'B', 'unit symbol' );
 	}
 
 	foreach ( $quant as $unit => $mag ) {
-		if ( (float) $bytes >= $mag ) {
+		if ( $bytes >= $mag ) {
 			return number_format_i18n( $bytes / $mag, $decimals ) . ' ' . $unit;
 		}
 	}
diff --git a/tests/phpstan/baselines/argument.type.neon b/tests/phpstan/baselines/argument.type.neon
index fb48bd1be342a..66bfb6d6b9585 100644
--- a/tests/phpstan/baselines/argument.type.neon
+++ b/tests/phpstan/baselines/argument.type.neon
@@ -118,11 +118,6 @@ parameters:
 			identifier: argument.type
 			count: 1
 			path: ../../../src/wp-admin/includes/class-wp-site-health-auto-updates.php
-		-
-			message: '#^Parameter \#1 \$bytes of function size_format expects int\|string, float\|false given\.$#'
-			identifier: argument.type
-			count: 1
-			path: ../../../src/wp-admin/includes/class-wp-site-health.php
 		-
 			message: '#^Parameter \#2 \$allowed_html of function wp_kses expects array\<array\>\|string, array\<string, array\<string, bool\>\|true\> given\.$#'
 			identifier: argument.type
diff --git a/tests/phpunit/tests/functions/sizeFormat.php b/tests/phpunit/tests/functions/sizeFormat.php
index 77134188634fe..b4a038408b47b 100644
--- a/tests/phpunit/tests/functions/sizeFormat.php
+++ b/tests/phpunit/tests/functions/sizeFormat.php
@@ -22,12 +22,26 @@ public function data_size_format() {
 		return array(
 			// Invalid values.
 			array( array(), 0, false ),
+			array( array( 'baba' ), 0, false ),
+			array( new stdClass(), 0, false ),
 			array( 'baba', 0, false ),
 			array( '', 0, false ),
+			array( '0x1A', 0, false ),
+			array( null, 0, false ),
+			array( true, 0, false ),
+			array( false, 0, false ),
 			array( '-1', 0, false ),
 			array( -1, 0, false ),
-			// Bytes.
+			array( -1.0, 0, false ),
+			// Zero bytes, in every numeric representation.
 			array( 0, 0, '0 B' ),
+			array( 0.0, 0, '0 B' ),
+			array( 0.0, 2, '0.00 B' ),
+			array( '0', 0, '0 B' ),
+			array( '0.0', 0, '0 B' ),
+			array( 0.0e3, 0, '0 B' ),
+			array( -0.0, 0, '0 B' ),
+			// Bytes.
 			array( 1, 0, '1 B' ),
 			array( 1023, 0, '1,023 B' ),
 			// Kilobytes.