diff --git a/include/clipp.h b/include/clipp.h
index d7b101e..efda1fa 100644
--- a/include/clipp.h
+++ b/include/clipp.h
@@ -45,7 +45,7 @@
 #include <utility>
 #include <iterator>
 #include <functional>
-
+#include <unordered_set>
 
 /*************************************************************************//**
  *
@@ -160,7 +160,7 @@ constexpr auto
 check_is_callable(int) -> decltype(
     std::declval<Fn>()(std::declval<Args>()...),
     std::integral_constant<bool,
-        std::is_same<Ret,typename std::result_of<Fn(Args...)>::type>::value>{} );
+        std::is_same_v<Ret, std::invoke_result_t<Fn, Args...>>>{} );
 
 template<class,class,class...>
 constexpr auto
@@ -171,7 +171,7 @@ constexpr auto
 check_is_callable_without_arg(int) -> decltype(
     std::declval<Fn>()(),
     std::integral_constant<bool,
-        std::is_same<Ret,typename std::result_of<Fn()>::type>::value>{} );
+        std::is_same_v<Ret, std::invoke_result_t<Fn>>>{} );
 
 template<class,class>
 constexpr auto
@@ -350,7 +350,7 @@ inline T clamped_on_limits(const V& v) {
 template<class T>
 struct make {
     static inline T from(const char* s) {
-        if(!s) return false;
+        if(!s) return T{};
         //a conversion from const char* to / must exist
         return static_cast<T>(s);
     }
@@ -6563,7 +6563,7 @@ class documentation
     doc_formatting usgFmt_;
     filter_function filter_;
     enum class paragraph { param, group };
-
+    mutable std::unordered_set<std::string> printed_param_keys_;
 
     /***************************************************************//**
      *
@@ -6578,6 +6578,7 @@ class documentation
         fos.hanging_indent(0);
         fos.paragraph_spacing(0);
         fos.ignore_newline_chars(fmt_.ignore_newline_chars());
+        printed_param_keys_.clear();
         print_doc(fos, cli_);
      }
 
@@ -6637,9 +6638,17 @@ class documentation
         else {
             const auto& p = ptrn.as_param();
             if(!filter_(p)) return;
+            
+            auto label = param_label(p, fmt_);
+            std::string key = label.c_str();
+            key += p.doc();
+
+            if (!printed_param_keys_.insert(key).second) {
+                return;
+            }
 
             handle_spacing(os, paragraph::param, indentLvl);
-            print_entry(os, param_label(p, fmt_), p.doc());
+            print_entry(os, label, p.doc());
         }
     }