diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 4cf32cbe..9ac43be6 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -63,7 +63,11 @@ jobs:
       Windowslatest:
         vmImage: 'windows-2019'
         cli11.std: 20
-        cli11.options: -DCMAKE_CXX_FLAG="/std:c++latest"
+        cli11.options: -DCMAKE_CXX_FLAGS="/std:c++latest /EHsc"
+      Linux17nortti:
+        vmImage: 'ubuntu-latest'
+        cli11.std: 17
+        cli11.options: -DCMAKE_CXX_FLAGS="-fno-rtti"
   pool:
     vmImage: $(vmImage)
   steps:
diff --git a/book/chapters/config.md b/book/chapters/config.md
index cfd570ac..153dc7c5 100644
--- a/book/chapters/config.md
+++ b/book/chapters/config.md
@@ -115,7 +115,8 @@ The default configuration file will read TOML files, but will write out files in
 ```cpp
 app.config_formatter(std::make_shared<CLI::ConfigTOML>());
 ```
-which makes use of a predefined modification of the ConfigBase class which INI also uses.
+
+which makes use of a predefined modification of the ConfigBase class which INI also uses. If a custom formatter is used that is not inheriting from the from ConfigBase class `get_config_formatter_base() will return a nullptr if RTTI is on (usually the default), or garbage if RTTI is off, so some care must be exercised in its use with custom configurations.
 
 ## Custom formats
 
diff --git a/include/CLI/App.hpp b/include/CLI/App.hpp
index 55d31dec..bd3bb82b 100644
--- a/include/CLI/App.hpp
+++ b/include/CLI/App.hpp
@@ -1314,15 +1314,15 @@ class App {
     int exit(const Error &e, std::ostream &out = std::cout, std::ostream &err = std::cerr) const {
 
         /// Avoid printing anything if this is a CLI::RuntimeError
-        if(dynamic_cast<const CLI::RuntimeError *>(&e) != nullptr)
+        if(e.get_name() == "RuntimeError")
             return e.get_exit_code();
 
-        if(dynamic_cast<const CLI::CallForHelp *>(&e) != nullptr) {
+        if(e.get_name() == "CallForHelp") {
             out << help();
             return e.get_exit_code();
         }
 
-        if(dynamic_cast<const CLI::CallForAllHelp *>(&e) != nullptr) {
+        if(e.get_name() == "CallForAllHelp") {
             out << help("", AppFormatMode::All);
             return e.get_exit_code();
         }
@@ -1524,7 +1524,12 @@ class App {
 
     /// Access the config formatter as a configBase pointer
     std::shared_ptr<ConfigBase> get_config_formatter_base() const {
+        // This is safer as a dynamic_cast if we have RTTI, as Config -> ConfigBase
+#if defined(__cpp_rtti) || (defined(__GXX_RTTI) && __GXX_RTTI) || (defined(_HAS_STATIC_RTTI) && (_HAS_STATIC_RTTI == 0))
         return std::dynamic_pointer_cast<ConfigBase>(config_formatter_);
+#else
+        return std::static_pointer_cast<ConfigBase>(config_formatter_);
+#endif
     }
 
     /// Get the app or subcommand description
diff --git a/include/CLI/Option.hpp b/include/CLI/Option.hpp
index 2e029303..55011cfb 100644
--- a/include/CLI/Option.hpp
+++ b/include/CLI/Option.hpp
@@ -506,7 +506,7 @@ class Option : public OptionBase<Option> {
 
     /// Can find a string if needed
     template <typename T = App> Option *needs(std::string opt_name) {
-        auto opt = dynamic_cast<T *>(parent_)->get_option_no_throw(opt_name);
+        auto opt = static_cast<T *>(parent_)->get_option_no_throw(opt_name);
         if(opt == nullptr) {
             throw IncorrectConstruction::MissingOption(opt_name);
         }
@@ -548,7 +548,7 @@ class Option : public OptionBase<Option> {
 
     /// Can find a string if needed
     template <typename T = App> Option *excludes(std::string opt_name) {
-        auto opt = dynamic_cast<T *>(parent_)->get_option_no_throw(opt_name);
+        auto opt = static_cast<T *>(parent_)->get_option_no_throw(opt_name);
         if(opt == nullptr) {
             throw IncorrectConstruction::MissingOption(opt_name);
         }
@@ -585,7 +585,7 @@ class Option : public OptionBase<Option> {
     template <typename T = App> Option *ignore_case(bool value = true) {
         if(!ignore_case_ && value) {
             ignore_case_ = value;
-            auto *parent = dynamic_cast<T *>(parent_);
+            auto *parent = static_cast<T *>(parent_);
             for(const Option_p &opt : parent->options_) {
                 if(opt.get() == this) {
                     continue;
@@ -610,7 +610,7 @@ class Option : public OptionBase<Option> {
 
         if(!ignore_underscore_ && value) {
             ignore_underscore_ = value;
-            auto *parent = dynamic_cast<T *>(parent_);
+            auto *parent = static_cast<T *>(parent_);
             for(const Option_p &opt : parent->options_) {
                 if(opt.get() == this) {
                     continue;