diff --git a/pkgs/top-level/php-packages.nix b/pkgs/top-level/php-packages.nix
index 1a438f6400aa..5de61dc5921e 100644
--- a/pkgs/top-level/php-packages.nix
+++ b/pkgs/top-level/php-packages.nix
@@ -417,7 +417,10 @@ lib.makeScope pkgs.newScope (
           #
           # These will be passed as arguments to mkExtension above.
           extensionData = [
-            { name = "bcmath"; }
+            {
+              name = "bcmath";
+              env.NIX_CFLAGS_COMPILE = "-std=gnu17";
+            }
             {
               name = "bz2";
               buildInputs = [ bzip2 ];