diff --git a/tests/libtest/lib1515.c b/tests/libtest/lib1515.c
index a786addb7..4ac9fcfdc 100644
--- a/tests/libtest/lib1515.c
+++ b/tests/libtest/lib1515.c
@@ -40,7 +40,7 @@
 #endif
 
 #define _MPRINTF_REPLACE
-#include "mprintf.h"
+#include <curl/mprintf.h>
 
 static int debug_callback(CURL *curl, curl_infotype info, char *msg, size_t len, void *ptr)
 {