diff --git a/src/collections.c b/src/collections.c
index 6b6dd8a..1a9e6df 100644
--- a/src/collections.c
+++ b/src/collections.c
@@ -14,10 +14,6 @@
 
 #include "php_collections.h"
 
-zend_string* collection_property_name;
-zend_string* pair_first_name;
-zend_string* pair_second_name;
-
 zend_object_handlers* collection_handlers;
 
 zend_class_entry* collections_collection_ce;
diff --git a/src/php_collections.h b/src/php_collections.h
index e3cd184..4fb3acd 100644
--- a/src/php_collections.h
+++ b/src/php_collections.h
@@ -25,10 +25,6 @@ extern zend_module_entry collections_module_entry;
 #define GC_DELREF(p) --GC_REFCOUNT(p)
 #endif
 
-extern zend_string* collection_property_name;
-extern zend_string* pair_first_name;
-extern zend_string* pair_second_name;
-
 extern PHP_COLLECTIONS_API zend_class_entry* collections_collection_ce;
 extern PHP_COLLECTIONS_API zend_class_entry* collections_pair_ce;