diff --git a/libdm/libdevmapper.h b/libdm/libdevmapper.h
index 02bf421b4..0786b3815 100644
--- a/libdm/libdevmapper.h
+++ b/libdm/libdevmapper.h
@@ -1291,6 +1291,7 @@ int dm_fclose(FILE *stream);
  */
 int dm_asprintf(char **buf, const char *format, ...)
     __attribute__ ((format(printf, 2, 3)));
+int dm_vasprintf(char **buf, const char *format, va_list ap);
 
 /*
  * create lockfile (pidfile) - create and lock a lock file
diff --git a/libdm/libdm-string.c b/libdm/libdm-string.c
index 776ec97e6..5ef633435 100644
--- a/libdm/libdm-string.c
+++ b/libdm/libdm-string.c
@@ -129,7 +129,7 @@ const char *dm_basename(const char *path)
 	return p ? p + 1 : path;
 }
 
-int dm_asprintf(char **result, const char *format, ...)
+int dm_vasprintf(char **result, const char *format, va_list aq)
 {
 	int i, n, size = 16;
 	va_list ap;
@@ -141,7 +141,7 @@ int dm_asprintf(char **result, const char *format, ...)
 		return -1;
 
 	for (i = 0;; i++) {
-		va_start(ap, format);
+		va_copy(ap, aq);
 		n = vsnprintf(buf, size, format, ap);
 		va_end(ap);
 
@@ -168,6 +168,16 @@ int dm_asprintf(char **result, const char *format, ...)
 	return n + 1;
 }
 
+int dm_asprintf(char **result, const char *format, ...)
+{
+	int r;
+	va_list ap;
+	va_start(ap, format);
+	r = dm_vasprintf(result, format, ap);
+	va_end(ap);
+	return r;
+}
+
 /*
  * Count occurences of 'c' in 'str' until we reach a null char.
  *