diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index ce510ac34..f20b6f3cc 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -2668,38 +2668,44 @@ void Tokenizer::setVarId()
             (Token::simpleMatch(tok->link(), ") {") || Token::Match(tok->link(), ") %type% {"))) {
             scopeInfo.push(variableId);
         } else if (tok->str() == "{") {
-            scopestartvarid.push(_varId);
-            if (Token::simpleMatch(tok->previous(), ")") || Token::Match(tok->tokAt(-2), ") %type%")) {
-                executableScope.push(true);
-            } else {
-                executableScope.push(executableScope.top());
-                scopeInfo.push(variableId);
+            // parse anonymous unions as part of the current scope
+            if (!(Token::simpleMatch(tok->previous(), "union") && Token::simpleMatch(tok->link(), "} ;"))) {
+                scopestartvarid.push(_varId);
+                if (Token::simpleMatch(tok->previous(), ")") || Token::Match(tok->tokAt(-2), ") %type%")) {
+                    executableScope.push(true);
+                } else {
+                    executableScope.push(executableScope.top());
+                    scopeInfo.push(variableId);
+                }
             }
         } else if (tok->str() == "}") {
-            // Set variable ids in class declaration..
-            if (!isC() && !executableScope.top() && tok->link()) {
-                setVarIdClassDeclaration(tok->link(),
-                                         variableId,
-                                         scopestartvarid.top(),
-                                         &structMembers,
-                                         &_varId);
-            }
+            // parse anonymous unions as part of the current scope
+            if (!(Token::simpleMatch(tok, "} ;") && Token::simpleMatch(tok->link()->previous(), "union {"))) {
+                // Set variable ids in class declaration..
+                if (!isC() && !executableScope.top() && tok->link()) {
+                    setVarIdClassDeclaration(tok->link(),
+                                             variableId,
+                                             scopestartvarid.top(),
+                                             &structMembers,
+                                             &_varId);
+                }
 
-            scopestartvarid.pop();
-            if (scopestartvarid.empty()) {  // should be impossible
-                scopestartvarid.push(0);
-            }
+                scopestartvarid.pop();
+                if (scopestartvarid.empty()) {  // should be impossible
+                    scopestartvarid.push(0);
+                }
 
-            if (scopeInfo.empty()) {
-                variableId.clear();
-            } else {
-                variableId.swap(scopeInfo.top());
-                scopeInfo.pop();
-            }
+                if (scopeInfo.empty()) {
+                    variableId.clear();
+                } else {
+                    variableId.swap(scopeInfo.top());
+                    scopeInfo.pop();
+                }
 
-            executableScope.pop();
-            if (executableScope.empty()) {   // should not possibly happen
-                executableScope.push(false);
+                executableScope.pop();
+                if (executableScope.empty()) {   // should not possibly happen
+                    executableScope.push(false);
+                }
             }
         }
 
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index eb3bf6365..f4443a0b2 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -252,6 +252,7 @@ private:
         TEST_CASE(varid_in_class8);     // unknown macro in class
         TEST_CASE(varid_in_class9);     // #4291 - id for variables accessed through 'this'
         TEST_CASE(varid_in_class10);
+        TEST_CASE(varid_in_class11);    // #4277 - anonymous union
         TEST_CASE(varid_initList);
         TEST_CASE(varid_operator);
         TEST_CASE(varid_throw);
@@ -3992,6 +3993,30 @@ private:
                            tokenizeDebugListing(code));
     }
 
+    void varid_in_class11() { // #4277 - anonymous union
+        const char code1[] = "class Foo {\n"
+                             "    union { float a; int b; };\n"
+                             "    void f() { a=0; }\n"
+                             "};";
+        ASSERT_EQUALS("\n\n##file 0\n"
+                      "1: class Foo {\n"
+                      "2: union { float a@1 ; int b@2 ; } ;\n"
+                      "3: void f ( ) { a@1 = 0 ; }\n"
+                      "4: } ;\n",
+                      tokenizeDebugListing(code1));
+
+        const char code2[] = "class Foo {\n"
+                             "    void f() { a=0; }\n"
+                             "    union { float a; int b; };\n"
+                             "};";
+        ASSERT_EQUALS("\n\n##file 0\n"
+                      "1: class Foo {\n"
+                      "2: void f ( ) { a@1 = 0 ; }\n"
+                      "3: union { float a@1 ; int b@2 ; } ;\n"
+                      "4: } ;\n",
+                      tokenizeDebugListing(code2));
+    }
+
 
     void varid_initList() {
         const char code[] = "class A {\n"