--- ./plugins/check_http.c.orig	2020-12-15 04:04:51 +0000
+++ ./plugins/check_http.c	2020-12-15 04:05:48 +0000
@@ -150,6 +150,28 @@
 
 extern int check_hostname;
 
+#ifndef HAVE_STRCASESTR
+char *
+strcasestr (const char *haystack, const char *needle)
+{
+      char *p, *startn = 0, *np = 0;
+
+      for (p = haystack; *p; p++) {
+              if (np) {
+                      if (toupper(*p) == toupper(*np)) {
+                              if (!*++np)
+                                      return startn;
+                      } else
+                              np = 0;
+              } else if (toupper(*p) == toupper(*needle)) {
+                      np = needle + 1;
+                      startn = p;
+              }
+      }
+
+      return 0;
+}
+#endif
 
 int
 main (int argc, char **argv)