diff --git a/lib/putenv.c b/lib/putenv.c
--- a/lib/putenv.c
+++ b/lib/putenv.c
@@ -34,6 +34,10 @@
 #include <string.h>
 #include <unistd.h>
 
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+# include <windows.h>
+#endif
+
 #if _LIBC
 # if HAVE_GNU_LD
 #  define environ __environ
@@ -67,6 +71,15 @@
 
   len = strlen (name);
 
+#if HAVE__PUTENV
+  {
+    char *name_x = malloc (len+2);
+    strcpy (name_x, name);
+    strcat (name_x, "=");
+    _putenv (name_x);
+    free (name_x);
+  }
+#else
   LOCK;
 
   ep = environ;
@@ -85,6 +98,7 @@
       ++ep;
 
   UNLOCK;
+#endif
 
   return 0;
 }
@@ -93,7 +107,7 @@
 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
    If STRING contains no '=', then remove STRING from the environment.  */
 int
-putenv (char *string)
+my_putenv (char *string)
 {
   const char *const name_end = strchr (string, '=');
   register size_t size;
@@ -123,6 +137,18 @@
         return _putenv (string);
       else
         {
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+          int putenv_result;
+          char *val;
+          size_t len = strlen (string);
+          char *name_x = malloc (len + 1);
+          strcpy (name_x, string);
+          name_x[name_end - string] = '\0';
+          val = &name_x[name_end - string + 1];
+          putenv_result = !SetEnvironmentVariable (name_x, val);
+          free (name_x);
+          return putenv_result;
+#else
           /* _putenv ("NAME=") unsets NAME, so invoke _putenv ("NAME=x")
              to allocate the environ vector and then replace the new
              entry with "NAME=".  */
@@ -144,6 +170,7 @@
           free (name_x);
           __set_errno (putenv_errno);
           return putenv_result;
+#endif
         }
 #else
       static char **last_environ = NULL;
@@ -160,7 +187,13 @@
 #endif
     }
   else
-    *ep = string;
+    {
+#if HAVE__PUTENV
+      _putenv (string);
+#else
+      *ep = string;
+#endif
+    }
 
   return 0;
 }