diff --git a/dlfcn/bug-dlsym1-lib1.c b/dlfcn/bug-dlsym1-lib1.c
index 5435b1f5ce..4eca2519fb 100644
--- a/dlfcn/bug-dlsym1-lib1.c
+++ b/dlfcn/bug-dlsym1-lib1.c
@@ -2,8 +2,10 @@
 
 extern int dlopen_test_variable;
 
+extern char foo (void);
+
 /* here to get the unresolved symbol in our .so */
-char foo()
+char foo(void)
 {
     return dlopen_test_variable;
 }