diff --git a/lldb/include/lldb/lldb-enumerations.h b/lldb/include/lldb/lldb-enumerations.h
--- a/lldb/include/lldb/lldb-enumerations.h
+++ b/lldb/include/lldb/lldb-enumerations.h
@@ -437,7 +437,10 @@
 /// specification for ease of use and consistency.
 /// The enum -> string code is in Language.cpp, don't change this
 /// table without updating that code as well.
-enum LanguageType : uint16_t {
+///
+/// This datatype is used in SBExpressionOptions::SetLanguage() which
+/// makes this type API. Do not change its underlying storage type!
+enum LanguageType {
   eLanguageTypeUnknown = 0x0000,        ///< Unknown or invalid language value.
   eLanguageTypeC89 = 0x0001,            ///< ISO C:1989.
   eLanguageTypeC = 0x0002,              ///< Non-standardized C, such as K&R.