diff --git a/cfg/std.cfg b/cfg/std.cfg
index b32b4cae74a..ab2516eee58 100644
--- a/cfg/std.cfg
+++ b/cfg/std.cfg
@@ -6645,6 +6645,7 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
   <function name="std::deque::push_back,std::deque::push_front,std::list::push_back,std::list::push_front,std::forward_list::push_front,std::queue::push,std::stack::push,std::vector::push_back">
     <noreturn>false</noreturn>
     <returnValue type="void"/>
+    <leak-ignore/>
     <arg nr="1">
       <not-uninit/>
     </arg>
diff --git a/lib/library.cpp b/lib/library.cpp
index f1058c7883a..4bb2aa94879 100644
--- a/lib/library.cpp
+++ b/lib/library.cpp
@@ -1010,8 +1010,12 @@ std::string Library::getFunctionName(const Token *ftok) const
     if (ftok->astParent()) {
         bool error = false;
         const Token * tok = ftok->astParent()->isUnaryOp("&") ? ftok->astParent()->astOperand1() : ftok->next()->astOperand1();
-        const std::string ret = getFunctionName(tok, error);
-        return error ? std::string() : ret;
+        std::string ret = getFunctionName(tok, error);
+        if (error)
+          return {};
+        if (startsWith(ret, "::"))
+            ret.erase(0, 2);
+        return ret;
     }
 
     // Lookup function name without using AST..
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 03b31da4bcc..6d4e9e6989d 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -9664,6 +9664,7 @@ void Tokenizer::simplifyNamespaceStd()
             continue;
         if (Token::Match(tok->previous(), ".|::|namespace"))
             continue;
+        const Library::Container* ctr{};
         if (Token::simpleMatch(tok->next(), "(")) {
             if (isFunctionHead(tok->next(), "{"))
                 userFunctions.insert(tok->str());
@@ -9681,7 +9682,7 @@ void Tokenizer::simplifyNamespaceStd()
             insert = true;
         else if (mSettings->library.hasAnyTypeCheck("std::" + tok->str()) ||
                  mSettings->library.podtype("std::" + tok->str()) ||
-                 mSettings->library.detectContainerOrIterator(tok, nullptr, /*withoutStd*/ true))
+                 ((ctr = mSettings->library.detectContainerOrIterator(tok, nullptr, /*withoutStd*/ true)) != nullptr && startsWith(ctr->startPattern, "std ::")))
             insert = true;
 
         if (insert) {
diff --git a/test/cfg/qt.cpp b/test/cfg/qt.cpp
index 2bef064a983..6a669953a70 100644
--- a/test/cfg/qt.cpp
+++ b/test/cfg/qt.cpp
@@ -71,6 +71,16 @@ bool QString7(QString s, const QString& l) {
     return l.startsWith(s);
 }
 
+namespace // #12355
+{
+    using namespace std;
+    QString QString_std(QString s)
+    {
+        s.replace("abc", "def");
+        return s;
+    }
+}
+
 void QByteArray1(QByteArray byteArrayArg)
 {
     for (int i = 0; i <= byteArrayArg.size(); ++i) {
diff --git a/test/cfg/std.cpp b/test/cfg/std.cpp
index 28279b77a6f..834ea0caa25 100644
--- a/test/cfg/std.cpp
+++ b/test/cfg/std.cpp
@@ -4860,3 +4860,9 @@ void std_vector_data_arithmetic()
     buf.resize(1);
     memcpy(buf.data() + 0, "", 1);
 }
+
+std::string global_scope_std() // #12355
+{
+    ::std::stringstream ss;
+    return ss.str();
+}
\ No newline at end of file