diff --git a/Modules/_json.c b/Modules/_json.c
index 2e39525..4da5e74 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -430,8 +430,8 @@
                 end += 6;
                 /* Decode 4 hex digits */
                 for (; next < end; next++) {
-                    c2 <<= 4;
                     Py_UNICODE digit = buf[next];
+                    c2 <<= 4;
                     switch (digit) {
                         case '0': case '1': case '2': case '3': case '4':
                         case '5': case '6': case '7': case '8': case '9':