diff --git a/src/functions/marshal_headers_from_sapi.php b/src/functions/marshal_headers_from_sapi.php
index 253f2c4b..ab493e22 100644
--- a/src/functions/marshal_headers_from_sapi.php
+++ b/src/functions/marshal_headers_from_sapi.php
@@ -35,13 +35,13 @@ function marshalHeadersFromSapi(array $server) : array
             }
         }
 
-        if (($value || $value === "0") && strpos($key, 'HTTP_') === 0) {
+        if ($value != '' && strpos($key, 'HTTP_') === 0) {
             $name = strtr(strtolower(substr($key, 5)), '_', '-');
             $headers[$name] = $value;
             continue;
         }
 
-        if ($value && strpos($key, 'CONTENT_') === 0) {
+        if ($value != '' && strpos($key, 'CONTENT_') === 0) {
             $name = 'content-' . strtolower(substr($key, 8));
             $headers[$name] = $value;
             continue;