diff --git a/tests/server/sockfilt.c b/tests/server/sockfilt.c
index e177c676e3..61cd235b5e 100644
--- a/tests/server/sockfilt.c
+++ b/tests/server/sockfilt.c
@@ -75,6 +75,9 @@
 #include <netdb.h>
 #endif
 
+#define ENABLE_CURLX_PRINTF
+/* make the curlx header define all printf() functions to use the curlx_*
+   versions instead */
 #include "curlx.h" /* from the private lib dir */
 #include "getpart.h"
 #include "inet_pton.h"
diff --git a/tests/server/sws.c b/tests/server/sws.c
index 852b27a2ed..161cea678f 100644
--- a/tests/server/sws.c
+++ b/tests/server/sws.c
@@ -55,6 +55,9 @@
 #include <netdb.h>
 #endif
 
+#define ENABLE_CURLX_PRINTF
+/* make the curlx header define all printf() functions to use the curlx_*
+   versions instead */
 #include "curlx.h" /* from the private lib dir */
 #include "getpart.h"
 #include "util.h"
diff --git a/tests/server/util.c b/tests/server/util.c
index 3fea37c46e..a3894cb44d 100644
--- a/tests/server/util.c
+++ b/tests/server/util.c
@@ -48,6 +48,9 @@
 #include <netdb.h>
 #endif
 
+#define ENABLE_CURLX_PRINTF
+/* make the curlx header define all printf() functions to use the curlx_*
+   versions instead */
 #include "curlx.h" /* from the private lib dir */
 #include "getpart.h"
 #include "util.h"