diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 540ec5ca5da..3a4b12c24e0 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -8690,7 +8690,6 @@ template<class F>
 static Result accumulateStructMembers(const Scope* scope, F f, ValueType::Accuracy accuracy, const Settings& settings)
 {
     size_t total = 0;
-    std::set<const Scope*> anonScopes;
     for (const Variable& var : scope->varlist) {
         if (var.isStatic())
             continue;
@@ -8701,12 +8700,7 @@ static Result accumulateStructMembers(const Scope* scope, F f, ValueType::Accura
             const MathLib::bigint dim = std::accumulate(var.dimensions().cbegin(), var.dimensions().cend(), MathLib::bigint(1), [](MathLib::bigint i1, const Dimension& dim) {
                 return i1 * dim.num;
             });
-            if (var.nameToken()->scope() != scope && var.nameToken()->scope()->definedType) { // anonymous union
-                const auto ret = anonScopes.insert(var.nameToken()->scope());
-                if (ret.second)
-                    total = f(total, *vt, dim, bits);
-            }
-            else if (vt->container && vt->container->startPattern == "std :: array <") {
+            if (vt->container && vt->container->startPattern == "std :: array <") {
                 const ValueType vtElement = ValueType::parseDecl(vt->containerTypeToken, settings);
                 total = f(total, vtElement, dim, bits);
             }
@@ -8840,7 +8834,8 @@ size_t ValueType::getSizeOf( const Settings& settings, Accuracy accuracy, SizeOf
                 currentBitfieldAlloc = 0;
                 currentBitCount = 0;
             }
-            return typeScope->type == ScopeType::eUnion ? std::max(total, n) : total + padding + n;
+            const bool isUnion = typeScope->type == ScopeType::eUnion || (vt2.typeScope && vt2.typeScope->nestedIn->type == ScopeType::eUnion && vt2.typeScope->nestedIn->className.empty());
+            return isUnion ? std::max(total, n) : total + padding + n;
         };
         Result result = accumulateStructMembers(typeScope, accHelper, accuracy, settings);
         size_t total = result.total;
diff --git a/test/testother.cpp b/test/testother.cpp
index e285d8d8bd0..32905364a06 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -2787,6 +2787,17 @@ class TestOther : public TestFixture {
               "}\n");
         ASSERT_EQUALS("", errout_str());
 
+        check("struct S {\n" // #15130
+              "    union {\n"
+              "        int i;\n"
+              "        struct {\n"
+              "            char a[24];\n"
+              "        } x;\n"
+              "    };\n"
+              "};\n"
+              "int f(S s) { return s.i; }\n");
+        ASSERT_EQUALS("[test.cpp:9:9]: (performance) Function parameter 's' should be passed by const reference. [passedByValue]\n", errout_str());
+
         /*const*/ Settings settingsWin64 = settingsBuilder().platform(Platform::Type::Win64).build();
         check("using ui64 = unsigned __int64;\n"
               "ui64 Test(ui64 one, ui64 two) { return one + two; }\n",
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 3609bf2aee2..e8b55bf6aae 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -1862,6 +1862,20 @@ class TestValueFlow : public TestFixture {
         ASSERT_EQUALS(1U, values.size());
         ASSERT_EQUALS(settings.platform.sizeof_int, values.back().intvalue);
         ASSERT_EQUALS_ENUM(ValueFlow::Value::ValueKind::Known, values.back().valueKind);
+
+        code = "struct S {\n"
+               "    union {\n"
+               "        int i;\n"
+               "        struct {\n"
+               "            char a[24];\n"
+               "        } x;\n"
+               "    };\n"
+               "};\n"
+               "int f() { return sizeof(S); }\n";
+        values = tokenValues(code, "( S");
+        ASSERT_EQUALS(1U, values.size());
+        ASSERT_EQUALS(24, values.back().intvalue);
+        ASSERT_EQUALS_ENUM(ValueFlow::Value::ValueKind::Known, values.back().valueKind);
     }
 
     void valueFlowComma()