diff --git a/pkgs/development/interpreters/php/default.nix b/pkgs/development/interpreters/php/default.nix
index b1fdb9e81f9..709f0fad41e 100644
--- a/pkgs/development/interpreters/php/default.nix
+++ b/pkgs/development/interpreters/php/default.nix
@@ -274,9 +274,10 @@ let
 
         #[[ -z "$libxml2" ]] || addToSearchPath PATH $libxml2/bin
 
+        export EXTENSION_DIR=$out/lib/php/extensions
+
         configureFlags+=(--with-config-file-path=$out/etc \
-          --includedir=$dev/include \
-          EXTENSION_DIR=$out/lib/php/extensions)
+          --includedir=$dev/include)
       '';
 
       configureFlags = [