diff --git a/rtc_base/stringencode.cc b/rtc_base/stringencode.cc
index df981b04a1..fc4e3bc8e7 100644
--- a/rtc_base/stringencode.cc
+++ b/rtc_base/stringencode.cc
@@ -60,9 +60,9 @@ char hex_encode(unsigned char val) {
 bool hex_decode(char ch, unsigned char* val) {
   if ((ch >= '0') && (ch <= '9')) {
     *val = ch - '0';
-  } else if ((ch >= 'A') && (ch <= 'Z')) {
+  } else if ((ch >= 'A') && (ch <= 'F')) {
     *val = (ch - 'A') + 10;
-  } else if ((ch >= 'a') && (ch <= 'z')) {
+  } else if ((ch >= 'a') && (ch <= 'f')) {
     *val = (ch - 'a') + 10;
   } else {
     return false;
diff --git a/rtc_base/stringencode_unittest.cc b/rtc_base/stringencode_unittest.cc
index 9bdc592c29..f21c4cb78c 100644
--- a/rtc_base/stringencode_unittest.cc
+++ b/rtc_base/stringencode_unittest.cc
@@ -141,7 +141,8 @@ TEST_F(HexEncodeTest, TestDecodeTooShort) {
 
 // Test that decoding non-hex data fails.
 TEST_F(HexEncodeTest, TestDecodeBogusData) {
-  dec_res_ = hex_decode_with_delimiter(decoded_, sizeof(decoded_), "xyz", 3, 0);
+  dec_res_ =
+      hex_decode_with_delimiter(decoded_, sizeof(decoded_), "axyz", 4, 0);
   ASSERT_EQ(0U, dec_res_);
 }