diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 32ac35aff..e36082fe0 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -9573,7 +9573,7 @@ void Tokenizer::simplifyNamespaceStd()
 
     for (const Token* tok = Token::findsimplematch(list.front(), "using namespace std ;"); tok; tok = tok->next()) {
         bool insert = false;
-        if (Token::Match(tok, "%var% (") && !Token::Match(tok->previous(), ".|::") && stdFunctions.find(tok->str()) != stdFunctions.end())
+        if (Token::Match(tok, "%var% (") && !Token::Match(tok->previous(), ".|::") && !Token::Match(tok->linkAt(1)->next(), "%var%|{") && stdFunctions.find(tok->str()) != stdFunctions.end())
             insert = true;
         else if (Token::Match(tok, "%var% <") && !Token::Match(tok->previous(), ".|::") && stdTemplates.find(tok->str()) != stdTemplates.end())
             insert = true;
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index 82c771066..1cae4463b 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -7795,6 +7795,20 @@ private:
         static const char expected13[] = "try { }\n"
                                          "catch ( std :: exception & exception ) { }";
         ASSERT_EQUALS(expected13, tokenizeAndStringify(code13, false));
+
+        // #5773 (Don't prepend 'std ::' to function definitions)
+        static const char code14[] = "using namespace std;\n"
+                                     "class C {\n"
+                                     "    void search() {}\n"
+                                     "    void search() const {}\n"
+                                     "    void search() THROW_MACRO {}\n"
+                                     "};";
+        static const char expected14[] = "class C {\n"
+                                         "void search ( ) { }\n"
+                                         "void search ( ) const { }\n"
+                                         "void search ( ) THROW_MACRO { }\n"
+                                         "} ;";
+        ASSERT_EQUALS(expected14, tokenizeAndStringify(code14, false));
     }
 
     void microsoftMFC() {