diff --git a/tests/libtest/lib655.c b/tests/libtest/lib655.c
index 7ee12a3f7..f87191598 100644
--- a/tests/libtest/lib655.c
+++ b/tests/libtest/lib655.c
@@ -23,7 +23,7 @@
 
 #include "memdebug.h"
 
-const char TEST_DATA_STRING[] = "Test data";
+static const char TEST_DATA_STRING[] = "Test data";
 static int cb_count = 0;
 
 static int