diff --git a/compat/mingw.c b/compat/mingw.c
index cb0914af6c..f6c7ad7fd8 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1220,14 +1220,14 @@ 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];
@@ -1242,8 +1242,10 @@ 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 ca80be1bbe..828d97760c 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -209,6 +209,7 @@ 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
diff --git a/config.mak.uname b/config.mak.uname
index 8131c81985..462988e8ab 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -326,7 +326,6 @@ ifeq ($(uname_S),Windows)
 	NO_IPV6 = YesPlease
 	NO_UNIX_SOCKETS = YesPlease
 	NO_SETENV = YesPlease
-	NO_UNSETENV = YesPlease
 	NO_STRCASESTR = YesPlease
 	NO_STRLCPY = YesPlease
 	NO_MEMMEM = YesPlease
@@ -479,7 +478,6 @@ ifneq (,$(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_MEMMEM = YesPlease