diff --git a/include/wx/platform.h b/include/wx/platform.h
index 7e1124426e..d6c317db1f 100644
--- a/include/wx/platform.h
+++ b/include/wx/platform.h
@@ -403,6 +403,10 @@
 
 #    ifdef __EMX__
 #        define OS2EMX_PLAIN_CHAR
+#    endif
+#    if defined(__INNOTEK_LIBC__)
+        /* Ensure visibility of strnlen declaration */
+#        define _GNU_SOURCE
 #    endif
 
     /* define __HPUX__ for HP-UX where standard macro is __hpux */