diff --git a/internal/gc.h b/internal/gc.h
index cc5e1932f1..81ca1a51d8 100644
--- a/internal/gc.h
+++ b/internal/gc.h
@@ -247,6 +247,10 @@ void rb_gc_update_values(long n, VALUE *values);
 void *ruby_sized_xrealloc(void *ptr, size_t new_size, size_t old_size) RUBY_ATTR_RETURNS_NONNULL RUBY_ATTR_ALLOC_SIZE((2));
 void *ruby_sized_xrealloc2(void *ptr, size_t new_count, size_t element_size, size_t old_count) RUBY_ATTR_RETURNS_NONNULL RUBY_ATTR_ALLOC_SIZE((2, 3));
 void ruby_sized_xfree(void *x, size_t size);
+
+#if USE_SHARED_GC
+void ruby_load_external_gc_from_argv(int argc, char **argv);
+#endif
 RUBY_SYMBOL_EXPORT_END
 
 int rb_ec_stack_check(struct rb_execution_context_struct *ec);
diff --git a/main.c b/main.c
index ddfa0569a2..8ff7c53d9c 100644
--- a/main.c
+++ b/main.c
@@ -24,6 +24,9 @@
 #ifdef HAVE_LOCALE_H
 #include <locale.h>
 #endif
+#if USE_SHARED_GC
+#include "internal/gc.h"
+#endif
 
 #if defined RUBY_DEVEL && !defined RUBY_DEBUG_ENV
 # define RUBY_DEBUG_ENV 1
@@ -32,8 +35,6 @@
 # undef RUBY_DEBUG_ENV
 #endif
 
-void ruby_load_external_gc_from_argv(int argc, char **argv);
-
 static int
 rb_main(int argc, char **argv)
 {