diff --git a/src/include/ngspice/stringutil.h b/src/include/ngspice/stringutil.h
index bb372b6bd..ea3c1557f 100644
--- a/src/include/ngspice/stringutil.h
+++ b/src/include/ngspice/stringutil.h
@@ -3,11 +3,14 @@
  * 1999 E. Rouat
  ************/
 
+#ifndef ngspice_STRINGUTIL_H
+#define ngspice_STRINGUTIL_H
+
 #include "ngspice/config.h"
 #include "ngspice/bool.h"
 
-#ifndef ngspice_STRINGUTIL_H
-#define ngspice_STRINGUTIL_H
+#include <stdarg.h>
+
 
 int prefix(register char *p, register char *s);
 char * copy(const char *str);
@@ -24,6 +27,8 @@ char * gettok(char **s);
 char * gettok_instance(char **);
 char * gettok_char(char **s, char p, bool inc_p, bool nested);
 
+extern char *tvprintf(const char *fmt, va_list args);
+
 #ifdef __GNUC__
 extern char *tprintf(const char *fmt, ...) __attribute__ ((format (__printf__, 1, 2)));
 #else
diff --git a/src/misc/string.c b/src/misc/string.c
index 237f99bec..6035c8d95 100644
--- a/src/misc/string.c
+++ b/src/misc/string.c
@@ -53,24 +53,21 @@ copy_substring(const char *str, const char *end)
 }
 
 
-char*
-tprintf(const char *fmt, ...)
+char *
+tvprintf(const char *fmt, va_list args)
 {
     char buf[1024];
     char *p = buf;
     int size = sizeof(buf);
 
-    va_list args;
-
     for (;;) {
 
         int nchars;
+        va_list ap;
 
-        va_start(args, fmt);
-
-        nchars = vsnprintf(p, (size_t) size, fmt, args);
-
-        va_end(args);
+        va_copy(ap, args);
+        nchars = vsnprintf(p, (size_t) size, fmt, ap);
+        va_end(ap);
 
         if (nchars == -1) {     // compatibility to old implementations
             size *= 2;
@@ -91,6 +88,20 @@ tprintf(const char *fmt, ...)
 }
 
 
+char *
+tprintf(const char *fmt, ...)
+{
+    char *rv;
+    va_list ap;
+
+    va_start(ap, fmt);
+    rv = tvprintf(fmt, ap);
+    va_end(ap);
+
+    return rv;
+}
+
+
 /* Determine whether sub is a substring of str. */
 /* Like strstr( ) XXX */