diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index de3597a00..76fa236b2 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -1830,7 +1830,6 @@ namespace {
             tok2 = tok2->tokAt(-2);
         }
 
-        // todo: check using namespace
         std::string fullScope1 = scope1;
         if (!scope1.empty() && !qualification.empty())
             fullScope1 += " :: ";
@@ -1839,6 +1838,19 @@ namespace {
         if (scope == fullScope1)
             return true;
 
+        // check using namespace
+        if (!scopeList1.back().usingNamespaces.empty()) {
+            if (qualification.empty()) {
+                if (scopeList1.back().usingNamespaces.find(scope) != scopeList1.back().usingNamespaces.end())
+                    return true;
+            } else {
+                for (auto ns : scopeList1.back().usingNamespaces) {
+                    if (scope == ns + " :: " + qualification)
+                        return true;
+                }
+            }
+        }
+
         std::string newScope1 = scope1;
 
         // scopes didn't match so try higher scopes
@@ -2024,9 +2036,25 @@ bool Tokenizer::simplifyUsing()
                         continue;
 
                     // remove the qualification
-                    while (tok1->strAt(-1) == "::" && tok1->strAt(-2) == scope) {
-                        tok1->deletePrevious();
-                        tok1->deletePrevious();
+                    std::string fullScope = scope;
+                    while (tok1->strAt(-1) == "::") {
+                        if (fullScope == tok1->strAt(-2)) {
+                            tok1->deletePrevious();
+                            tok1->deletePrevious();
+                            break;
+                        } else {
+                            const std::string::size_type idx = fullScope.rfind(" ");
+
+                            if (idx == std::string::npos)
+                                break;
+
+                            if (tok1->strAt(-2) == fullScope.substr(idx + 1)) {
+                                tok1->deletePrevious();
+                                tok1->deletePrevious();
+                                fullScope.resize(idx - 3);
+                            } else
+                                break;
+                        }
                     }
 
                     Token * arrayStart = nullptr;
diff --git a/test/testsimplifyusing.cpp b/test/testsimplifyusing.cpp
index 83e081208..2372959bc 100644
--- a/test/testsimplifyusing.cpp
+++ b/test/testsimplifyusing.cpp
@@ -64,6 +64,7 @@ private:
         TEST_CASE(simplifyUsing8976);
         TEST_CASE(simplifyUsing9040);
         TEST_CASE(simplifyUsing9042);
+        TEST_CASE(simplifyUsing9191);
     }
 
     std::string tok(const char code[], bool simplify = true, Settings::PlatformType type = Settings::Native, bool debugwarnings = true) {
@@ -494,6 +495,35 @@ private:
         ASSERT_EQUALS(exp, tok(code, true, Settings::Win64));
     }
 
+    void simplifyUsing9191() {
+        const char code[] = "namespace NS1 {\n"
+                            "  namespace NS2 {\n"
+                            "    using _LONG = signed long long;\n"
+                            "  }\n"
+                            "}\n"
+                            "void f1() {\n"
+                            "  using namespace NS1;\n"
+                            "  NS2::_LONG A;\n"
+                            "}\n"
+                            "void f2() {\n"
+                            "  using namespace NS1::NS2;\n"
+                            "  _LONG A;\n"
+                            "}";
+
+        const char exp[] = "namespace NS1 { "
+                           "} "
+                           "void f1 ( ) { "
+                           "using namespace NS1 ; "
+                           "signed long long A ; "
+                           "} "
+                           "void f2 ( ) { "
+                           "using namespace NS1 :: NS2 ; "
+                           "signed long long A ; "
+                           "}";
+
+        ASSERT_EQUALS(exp, tok(code, false));
+    }
+
 };
 
 REGISTER_TEST(TestSimplifyUsing)