diff --git a/src/ChunkedEncoding.h b/src/ChunkedEncoding.h
index a83b216a6..5b959ad30 100644
--- a/src/ChunkedEncoding.h
+++ b/src/ChunkedEncoding.h
@@ -44,28 +44,26 @@ namespace uWS {
     inline void consumeHexNumber(std::string_view &data, uint64_t &state) {
         /* Consume everything higher than 32 */
         while (data.length() && data.data()[0] > 32) {
-    
+
             unsigned char digit = (unsigned char)data.data()[0];
-            unsigned int number;
-    
-            if (digit >= '0' && digit <= '9') {
-                number = (unsigned int) (digit - '0');
-            } else if (digit >= 'a' && digit <= 'f') {
-                number = (unsigned int) (digit - 'a') + 10;
-            } else if (digit >= 'A' && digit <= 'F') {
-                number = (unsigned int) (digit - 'A') + 10;
-            } else {
-                /* Not a hex digit: chunk-size token ends here (chunk-ext follows) */
-                break;
+            if (digit >= 'a') {
+                digit = (unsigned char) (digit - ('a' - ':'));
+            } else if (digit >= 'A') {
+                digit = (unsigned char) (digit - ('A' - ':'));
             }
-    
-            if (chunkSize(state) & STATE_SIZE_OVERFLOW) {
+
+            unsigned int number = ((unsigned int) digit - (unsigned int) '0');
+
+            if (number > 16 || (chunkSize(state) & STATE_SIZE_OVERFLOW)) {
                 state = STATE_IS_ERROR;
                 return;
             }
-    
-            uint64_t bits = STATE_IS_CHUNKED;
+
+            // extract state bits
+            uint64_t bits = /*state &*/ STATE_IS_CHUNKED;
+
             state = (state & STATE_SIZE_MASK) * 16ull + number;
+
             state |= bits;
             data.remove_prefix(1);
         }