diff --git a/src/core/def.c b/src/core/def.c
index 9da36fee..282fb41d 100644
--- a/src/core/def.c
+++ b/src/core/def.c
@@ -118,6 +118,29 @@ lwip_strnstr(const char *buffer, const char *token, size_t n)
 }
 #endif
 
+#ifndef lwip_strnistr
+/**
+ * @ingroup sys_nonstandard
+ * lwIP default implementation for strnistr() non-standard function.
+ * This can be \#defined to strnistr() depending on your platform port.
+ */
+char *
+lwip_strnistr(const char *buffer, const char *token, size_t n)
+{
+  const char *p;
+  size_t tokenlen = strlen(token);
+  if (tokenlen == 0) {
+    return LWIP_CONST_CAST(char *, buffer);
+  }
+  for (p = buffer; *p && (p + tokenlen <= buffer + n); p++) {
+    if (lwip_strnicmp(p, token, tokenlen) == 0) {
+      return LWIP_CONST_CAST(char *, p);
+    }
+  }
+  return NULL;
+}
+#endif
+
 #ifndef lwip_stricmp
 /**
  * @ingroup sys_nonstandard
diff --git a/src/include/lwip/def.h b/src/include/lwip/def.h
index dfb266d1..d6bf7630 100644
--- a/src/include/lwip/def.h
+++ b/src/include/lwip/def.h
@@ -144,6 +144,10 @@ int   lwip_stricmp(const char* str1, const char* str2);
 /* This can be #defined to strnstr() depending on your platform */
 char* lwip_strnstr(const char* buffer, const char* token, size_t n);
 #endif
+#ifndef lwip_strnistr
+/* This can be #defined to strnistr() depending on your platform */
+char* lwip_strnistr(const char* buffer, const char* token, size_t n);
+#endif
 
 #ifdef __cplusplus
 }