diff --git a/ChangeLog b/ChangeLog
index 7c9db7120..c17e906e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2005-04-09  Moritz Bunkus  <moritz@bunkus.org>
+
+	* all: bug fix: My output functions did not work on AMD64
+	systems. Fixes Anthill bug 120.
+
 2005-04-07  Moritz Bunkus  <moritz@bunkus.org>
 
 	* mkvextract: new feature: Added the extraction of the raw
diff --git a/src/common/common.cpp b/src/common/common.cpp
index 1e68c3447..ed525b1f3 100644
--- a/src/common/common.cpp
+++ b/src/common/common.cpp
@@ -1266,7 +1266,7 @@ mxprints(char *dst,
 static void
 mxmsg(int level,
       const char *fmt,
-      va_list &ap) {
+      va_list ap) {
   string new_fmt, output;
   bool nl;
   FILE *stream;
@@ -1397,7 +1397,11 @@ get_varg_len(const char *fmt,
   size = 1024;
   dst = (char *)safemalloc(size);
   while (1) {
-    result = vsnprintf(dst, size - 1, fmt, ap);
+    va_list ap2;
+
+    va_copy(ap2, ap);
+    result = vsnprintf(dst, size - 1, fmt, ap2);
+    va_end(ap2);
     if (result >= 0) {
       safefree(dst);
       return result;
@@ -1412,16 +1416,18 @@ get_varg_len(const char *fmt,
 
 string
 mxvsprintf(const char *fmt,
-           va_list &ap) {
+           va_list ap) {
   string new_fmt, dst;
   char *new_string;
   int len;
+  va_list ap2;
 
   fix_format(fmt, new_fmt);
   len = get_varg_len(new_fmt.c_str(), ap);
   new_string = (char *)safemalloc(len + 1);
-  vsprintf(new_string, new_fmt.c_str(), ap);
-  va_end(ap);
+  va_copy(ap2, ap);
+  vsprintf(new_string, new_fmt.c_str(), ap2);
+  va_end(ap2);
   dst = new_string;
   safefree(new_string);
 
diff --git a/src/common/common.h b/src/common/common.h
index b79699522..7803e2ef4 100644
--- a/src/common/common.h
+++ b/src/common/common.h
@@ -131,7 +131,7 @@ void MTX_DLL_API mxverb(int level, const char *fmt, ...);
 void MTX_DLL_API mxdebug(const char *fmt, ...);
 int MTX_DLL_API mxsscanf(const string &str, const char *fmt, ...);
 #endif
-string MTX_DLL_API mxvsprintf(const char *fmt, va_list &ap);
+string MTX_DLL_API mxvsprintf(const char *fmt, va_list ap);
 void MTX_DLL_API mxexit(int code = -1);
 
 #define trace() _trace(__func__, __FILE__, __LINE__)