diff --git a/PC/config.c b/PC/config.c
index f295f85..0ff4c93 100644
--- a/PC/config.c
+++ b/PC/config.c
@@ -43,6 +43,9 @@
 #endif
 extern void initcmath();
 extern void initerrno();
+#ifdef WITH_CYCLE_GC
+extern void initgc();
+#endif
 #ifndef MS_WIN64
 extern void initimageop();
 #endif
@@ -89,6 +92,9 @@
 #endif
         {"cmath", initcmath},
         {"errno", initerrno},
+#ifdef WITH_CYCLE_GC
+        {"gc", initgc},
+#endif
 #ifndef MS_WIN64
         {"imageop", initimageop},
 #endif
diff --git a/PC/config.h b/PC/config.h
index dfe5118..43bb35f 100644
--- a/PC/config.h
+++ b/PC/config.h
@@ -451,6 +451,9 @@
 /* Define if you want to use the GNU readline library */
 /* #define WITH_READLINE 1 */
 
+/* Define if you want cycle garbage collection */
+/* #define WITH_CYCLE_GC 1 */
+
 /* Define if you have clock.  */
 /* #define HAVE_CLOCK */