diff --git a/ext/otel_observer.c b/ext/otel_observer.c
index b3138d1..a10e97c 100644
--- a/ext/otel_observer.c
+++ b/ext/otel_observer.c
@@ -9,6 +9,7 @@
 #include "php_opentelemetry.h"
 
 static int op_array_extension = -1;
+static int internal_function_extension = -1;
 
 const char *withspan_fqn_lc = "opentelemetry\\api\\instrumentation\\withspan";
 const char *spanattribute_fqn_lc =
@@ -1149,5 +1150,7 @@ void opentelemetry_observer_init(INIT_FUNC_ARGS) {
         zend_observer_fcall_register(observer_fcall_init);
         op_array_extension =
             zend_get_op_array_extension_handle("opentelemetry");
+        internal_function_extension =
+            zend_get_internal_function_extension_handle("opentelemetry");
     }
 }