diff --git a/src/core/lib/support/string.c b/src/core/lib/support/string.c
index f263f82bafe..426fce28f87 100644
--- a/src/core/lib/support/string.c
+++ b/src/core/lib/support/string.c
@@ -279,7 +279,8 @@ int gpr_stricmp(const char *a, const char *b) {
 void *gpr_memrchr(const void *s, int c, size_t n) {
   if (s == NULL) return NULL;
   char *b = (char *)s;
-  for (size_t i = 0; i < n; i++) {
+  size_t i;
+  for (i = 0; i < n; i++) {
     if (b[n - i - 1] == c) {
       return &b[n - i - 1];
     }