diff --git a/hw/dmx/config/dmxparse.h b/hw/dmx/config/dmxparse.h
index 7d31b6309..cc2f0eb71 100644
--- a/hw/dmx/config/dmxparse.h
+++ b/hw/dmx/config/dmxparse.h
@@ -38,6 +38,7 @@
 #define _DMXPARSE_H_
 
 #include <stdio.h>              /* For FILE */
+#include <X11/Xfuncproto.h>     /* For _X_ATTRIBUTE_PRINTF */
 
 /** Stores tokens not stored in other structures (e.g., keywords and ;) */
 typedef struct _DMXConfigToken {
@@ -203,7 +204,7 @@ extern int yylex(void);
 extern int yydebug;
 extern void yyerror(const char *message);
 
-extern void dmxConfigLog(const char *format, ...);
+extern void dmxConfigLog(const char *format, ...) _X_ATTRIBUTE_PRINTF(1,0);
 extern void *dmxConfigAlloc(unsigned long bytes);
 extern void *dmxConfigRealloc(void *orig,
                               unsigned long orig_bytes, unsigned long bytes);
diff --git a/hw/dmx/config/dmxprint.c b/hw/dmx/config/dmxprint.c
index 9dec52b5c..536d92bfe 100644
--- a/hw/dmx/config/dmxprint.c
+++ b/hw/dmx/config/dmxprint.c
@@ -130,7 +130,7 @@ dmxConfigPopState(void)
     dmxConfigNewline();
 }
 
-static void
+static void _X_ATTRIBUTE_PRINTF(4, 5)
 dmxConfigOutput(int addSpace, int doNewline, const char *comment,
                 const char *format, ...)
 {