diff --git a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
index 6374c7a4..b017e109 100644
--- a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
@@ -380,8 +380,8 @@ void HeaderSearchDirs::addDefines ( std::vector<std::string> & defines ) {
 
     // Add -D command line arguments as well as "#define TRICK_ICG" to the preprocessor
     unsigned int ii ;
-    std::string predefines("#define TRICK_ICG\n") ;
-    predefines += "#define __STRICT_ANSI__\n" ;
+    std::string predefines("#define TRICK_ICG\n");
+    predefines += "#define __STRICT_ANSI__\n";
     for ( ii = 0 ; ii < defines.size() ; ii++ ) {
         size_t found = defines[ii].find("=") ;
         if ( found != defines[ii].npos ) {
@@ -392,7 +392,6 @@ void HeaderSearchDirs::addDefines ( std::vector<std::string> & defines ) {
         predefines += std::string("#define ") + defines[ii] + "\n" ;
     }
     pp.setPredefines(pp.getPredefines() + "\n" + predefines) ;
-
 }
 
 void HeaderSearchDirs::addTrickICGFoundFile ( std::string file_name ) {
diff --git a/trick_source/codegen/Interface_Code_Gen/main.cpp b/trick_source/codegen/Interface_Code_Gen/main.cpp
index 35a2e019..d16514e9 100644
--- a/trick_source/codegen/Interface_Code_Gen/main.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/main.cpp
@@ -51,6 +51,24 @@ llvm::cl::alias compat15_alias ("compat15" , llvm::cl::desc("Alias for -c") , ll
 llvm::cl::opt<bool> m32("m32", llvm::cl::desc("Generate io code for use with 32bit mode"), llvm::cl::init(false), llvm::cl::ZeroOrMore) ;
 
 
+void set_lang_opts(clang::CompilerInstance & ci) {
+    ci.getLangOpts().CXXExceptions = true ;
+    // Activate C++11 parsing
+    ci.getLangOpts().Bool = true ;
+    ci.getLangOpts().WChar = true ;
+    ci.getLangOpts().CPlusPlus = true ;
+    ci.getLangOpts().CPlusPlus11 = true ;
+    ci.getLangOpts().CXXOperatorNames = true ;
+#if (LIBCLANG_MAJOR >= 6)
+    ci.getLangOpts().CPlusPlus14 = true ;
+    ci.getLangOpts().DoubleSquareBracketAttributes = true ;
+#endif
+    // Activate C++17 parsing
+#if (LIBCLANG_MAJOR >= 10)
+    ci.getLangOpts().GNUCVersion = true ;
+    ci.getLangOpts().CPlusPlus17 = true ;
+#endif
+}
 /**
 Most of the main program is pieced together from examples on the web. We are doing the following:
 
@@ -99,19 +117,7 @@ int main(int argc, char * argv[]) {
     ci.createDiagnostics();
     ci.getDiagnosticOpts().ShowColors = 1 ;
     ci.getDiagnostics().setIgnoreAllWarnings(true) ;
-    ci.getLangOpts().CXXExceptions = true ;
-    // Activate C++11 parsing
-    ci.getLangOpts().Bool = true ;
-    ci.getLangOpts().WChar = true ;
-    ci.getLangOpts().CPlusPlus = true ;
-    ci.getLangOpts().CPlusPlus11 = true ;
-#if (LIBCLANG_MAJOR >= 6)
-    ci.getLangOpts().CPlusPlus14 = true ;
-#endif
-    ci.getLangOpts().CXXOperatorNames = true ;
-#if (LIBCLANG_MAJOR >= 6)
-    ci.getLangOpts().DoubleSquareBracketAttributes = true ;
-#endif
+    set_lang_opts(ci);
 
     // Create all of the necessary managers.
     ci.createFileManager();
@@ -157,14 +163,17 @@ int main(int argc, char * argv[]) {
 #else
     clang::CompilerInvocation::setLangDefaults(ci.getLangOpts(), clang::IK_CXX, trip, ppo) ;
 #endif
-    // setting the language defaults clears the c++11 flag.
-    ci.getLangOpts().CPlusPlus11 = true ;
-#if (LIBCLANG_MAJOR >= 6)
-    ci.getLangOpts().CPlusPlus14 = true ;
-#endif
+
+    // setting the language defaults clears some of the language opts, set them again.
+    set_lang_opts(ci);
+
 #endif
     clang::Preprocessor& pp = ci.getPreprocessor();
 
+#if (LIBCLANG_MAJOR >= 10)
+    clang::InitializePreprocessor(pp, ppo, ci.getPCHContainerReader(), ci.getFrontendOpts());
+#endif
+
     // Add all of the include directories to the preprocessor
     HeaderSearchDirs hsd(ci.getPreprocessor().getHeaderSearchInfo(), ci.getHeaderSearchOpts(), pp, sim_services_flag);
     hsd.addSearchDirs(include_dirs, isystem_dirs);