diff --git a/display/vt11.c b/display/vt11.c
index 2d5c6ee0..dee39e6e 100644
--- a/display/vt11.c
+++ b/display/vt11.c
@@ -144,9 +144,9 @@ extern "C" {
 int vt11_debug;
 
 #if defined(VM_PDP11)
-extern void _sim_debug (unsigned int dbits, DEVICE* dptr, const char* fmt, ...);
+extern void _sim_debug_device (unsigned int dbits, DEVICE* dptr, const char* fmt, ...);
 
-#define DEBUGF(...) _sim_debug (vt11_dbit, vt11_dptr, ##  __VA_ARGS__)
+#define DEBUGF(...) _sim_debug_device (vt11_dbit, vt11_dptr, ##  __VA_ARGS__)
 #else /* DEBUG_VT11 */
 #define DEBUGF(...) do {if (vt11_debug & DBG_CALL) { printf(##  __VA_ARGS__); fflush(stdout); };} while (0)
 #endif /* defined(DEBUG_VT11) || defined(VM_PDP11) */