diff --git a/sanei/sanei_init_debug.c b/sanei/sanei_init_debug.c
index 6b50f0364..a4e7b8e25 100644
--- a/sanei/sanei_init_debug.c
+++ b/sanei/sanei_init_debug.c
@@ -41,6 +41,7 @@
 #include "../include/sane/config.h"
 
 #include <ctype.h>
+#include <locale.h>
 #include <stdio.h>
 #include <stdlib.h>
 #ifdef HAVE_UNISTD_H
@@ -70,12 +71,14 @@
 void
 sanei_init_debug (const char * backend, int * var)
 {
+  char *lc_ctype;
   char ch, buf[256] = "SANE_DEBUG_";
   const char * val;
   unsigned int i;
 
   *var = 0;
 
+  lc_ctype = setlocale (LC_CTYPE, "C");
   for (i = 11; (ch = backend[i - 11]) != 0; ++i)
     {
       if (i >= sizeof (buf) - 1)
@@ -83,6 +86,7 @@ sanei_init_debug (const char * backend, int * var)
       buf[i] = toupper(ch);
     }
   buf[i] = '\0';
+  setlocale (LC_CTYPE, lc_ctype);
 
   val = getenv (buf);