--- a/security/certverifier/tests/gtest/CTTestUtils.cpp
+++ b/security/certverifier/tests/gtest/CTTestUtils.cpp
@@ -120,16 +120,17 @@ CharToByte(char c)
   if (c >= '0' && c <= '9') {
     return c - '0';
   } else if (c >= 'a' && c <= 'f') {
     return c - 'a' + 10;
   } else if (c >= 'A' && c <= 'F') {
     return c - 'A' + 10;
   }
   MOZ_RELEASE_ASSERT(false);
+  return 0;
 }
 
 static Buffer
 HexToBytes(const char* hexData)
 {
   size_t hexLen = strlen(hexData);
   MOZ_RELEASE_ASSERT(hexLen > 0 && (hexLen % 2 == 0));
   size_t resultLen = hexLen / 2;