diff --git a/builder/frameworks/realtek-ambz-sdk.py b/builder/frameworks/realtek-ambz-sdk.py
index ec5d6c7..3721300 100644
--- a/builder/frameworks/realtek-ambz-sdk.py
+++ b/builder/frameworks/realtek-ambz-sdk.py
@@ -194,8 +194,8 @@ env.AddLibrary(
     ],
 )
 
-# Sources - lwIP 2.0.0
-env.AddLibraryLwIP(version="2.0.0", port="amb1")
+# Sources - lwIP 2.1.3
+env.AddLibraryLwIP(version="2.1.3", port="amb1")
 
 # Sources - mbedTLS
 env.AddLibrary(
diff --git a/builder/main.py b/builder/main.py
index ea07f21..d2f8c69 100644
--- a/builder/main.py
+++ b/builder/main.py
@@ -27,7 +27,6 @@ if env.get("PROGNAME", "program") == "program":
     env.Replace(PROGNAME="firmware")
 env.Replace(PROGSUFFIX=".elf")
 
-# Toolchain config - TODO multiple arch, specified in board.json
 prefix = board.get("build.prefix", "")
 env.Replace(
     AR=prefix + "gcc-ar",
diff --git a/platform.json b/platform.json
index 6f0db2f..e838ddb 100644
--- a/platform.json
+++ b/platform.json
@@ -49,7 +49,7 @@
       "toolchain": "gccarmnoneeabi@~1.50201.0",
       "libraries": {
         "lwip": [
-          "v2.0.0-amb1"
+          "v2.1.3-amb1"
         ]
       }
     },
diff --git a/platform/realtek-ambz/fixups/inc/strproc.h b/platform/realtek-ambz/fixups/inc/strproc.h
new file mode 100644
index 0000000..21e8b45
--- /dev/null
+++ b/platform/realtek-ambz/fixups/inc/strproc.h
@@ -0,0 +1,22 @@
+/* Copyright (c) Kuba Szczodrzyński 2022-11-26. */
+
+// make <strproc.h> not #define isprint, isdigit, isxdigit, islower and isspace
+// this conflicts with stdlib <ctype.h>, if <strproc.h> is included before it
+
+// include <ctype.h> before to get all its macros
+#include <ctype.h>
+
+// make 'static inline int _tolower' unused
+#undef _tolower
+#define _tolower _tolower_dummy
+
+#include_next <strproc.h>
+
+// restore _tolower to ctype's macro
+#undef _tolower
+#define _tolower(__c) ((unsigned char)(__c) - 'A' + 'a')
+
+// dirty fix for compiling mbedTLS which uses _B as variable name
+#ifdef CONFIG_SSL_RSA
+#undef _B
+#endif
\ No newline at end of file