diff --git a/pkgs/development/tools/misc/blackfire/php-probe.nix b/pkgs/development/tools/misc/blackfire/php-probe.nix
index 39f5dd5185f4..960928c24552 100644
--- a/pkgs/development/tools/misc/blackfire/php-probe.nix
+++ b/pkgs/development/tools/misc/blackfire/php-probe.nix
@@ -9,6 +9,8 @@
 , common-updater-scripts
 }:
 
+assert lib.assertMsg (!php.ztsSupport) "blackfire only supports non zts versions of PHP";
+
 let
   phpMajor = lib.versions.majorMinor php.version;