diff --git a/Makefile b/Makefile
index ad13177ead..9de2210e77 100644
--- a/Makefile
+++ b/Makefile
@@ -1244,7 +1244,6 @@ ifeq ($(uname_S),Windows)
 	NO_IPV6 = YesPlease
 	NO_UNIX_SOCKETS = YesPlease
 	NO_SETENV = YesPlease
-	NO_UNSETENV = YesPlease
 	NO_STRCASESTR = YesPlease
 	NO_STRLCPY = YesPlease
 	NO_STRTOK_R = YesPlease
@@ -1395,7 +1394,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_SYMLINK_HEAD = YesPlease
 	NO_UNIX_SOCKETS = YesPlease
 	NO_SETENV = YesPlease
-	NO_UNSETENV = YesPlease
 	NO_STRCASESTR = YesPlease
 	NO_STRLCPY = YesPlease
 	NO_STRTOK_R = YesPlease
diff --git a/compat/mingw.c b/compat/mingw.c
index 1bde0d9201..c1e554015f 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1263,14 +1263,14 @@ static char **env_setenv(char **env, const char *name)
 			for (i = 0; env[i]; i++)
 				;
 			env = xrealloc(env, (i+2)*sizeof(*env));
-			env[i] = xstrdup(name);
+			env[i] = (char*) name;
 			env[i+1] = NULL;
 		}
 	}
 	else {
 		free(env[i]);
 		if (*eq)
-			env[i] = xstrdup(name);
+			env[i] = (char*) name;
 		else
 			for (; env[i]; i++)
 				env[i] = env[i+1];
@@ -1285,8 +1285,10 @@ char **make_augmented_environ(const char *const *vars)
 {
 	char **env = copy_environ();
 
-	while (*vars)
-		env = env_setenv(env, *vars++);
+	while (*vars) {
+		const char *v = *vars++;
+		env = env_setenv(env, strchr(v, '=') ? xstrdup(v) : v);
+	}
 	return env;
 }
 
diff --git a/compat/mingw.h b/compat/mingw.h
index 8980101ba1..e6ce0bcb7a 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -202,6 +202,7 @@ char *mingw_getenv(const char *name);
 #define getenv mingw_getenv
 int mingw_putenv(const char *namevalue);
 #define putenv mingw_putenv
+#define unsetenv mingw_putenv
 
 int mingw_gethostname(char *host, int namelen);
 #define gethostname mingw_gethostname