diff --git a/Source/Model/Classes/NMR_ModelMetaDataGroup.cpp b/Source/Model/Classes/NMR_ModelMetaDataGroup.cpp
index 08e1f841b..e3265d347 100644
--- a/Source/Model/Classes/NMR_ModelMetaDataGroup.cpp
+++ b/Source/Model/Classes/NMR_ModelMetaDataGroup.cpp
@@ -113,7 +113,11 @@ namespace NMR {
 			std::string sName;
 			std::string sValue;
 			PModelMetaData metaData = pSourceMetaDataGroup->getMetaData(nIndex);
-			addMetaData(metaData->getNameSpace(), metaData->getName(), metaData->getValue(), metaData->getType(), metaData->getPreserve());
+
+			// only add metadata, if the key does not exist yet
+			if (!hasMetaData(metaData->getKey())) {
+				addMetaData(metaData->getNameSpace(), metaData->getName(), metaData->getValue(), metaData->getType(), metaData->getPreserve());
+			}
 		}
 	}
 }
diff --git a/Tests/CPP_Bindings/Source/Volumetric.cpp b/Tests/CPP_Bindings/Source/Volumetric.cpp
index 9518750ab..e60448c47 100644
--- a/Tests/CPP_Bindings/Source/Volumetric.cpp
+++ b/Tests/CPP_Bindings/Source/Volumetric.cpp
@@ -1258,7 +1258,7 @@ namespace Lib3MF
         auto const reader = sourceModel->QueryReader("3mf");
         reader->ReadFromFile(InFolder + "SphereInACage.3mf");
 
-        auto sourcetModelFunctionCount = sourceModel->GetFunctions()->Count();
+        auto sourceModelFunctionCount = sourceModel->GetFunctions()->Count();
 
         auto const targetModel = wrapper->CreateModel();
 
@@ -1268,7 +1268,31 @@ namespace Lib3MF
         targetModel->MergeFromModel(sourceModel.get());
 
         auto targetFunctionsIter = targetModel->GetFunctions();
-        EXPECT_EQ(targetFunctionsIter->Count(), sourcetModelFunctionCount + 1);
+        EXPECT_EQ(targetFunctionsIter->Count(), sourceModelFunctionCount + 1);
+    }
+
+     TEST_F(Volumetric,
+           Volumetric_Merge_FunctionsFromLoadedModelIntoLoadedTargetModel_FunctionCountIncreases)
+    {
+        // load the source model
+        auto const sourceModel = wrapper->CreateModel();
+        auto reader = sourceModel->QueryReader("3mf");
+        reader->SetStrictModeActive(true);
+        reader->ReadFromFile(InFolder + "SphereInACage.3mf");
+
+        auto sourceModelFunctionCount = sourceModel->GetFunctions()->Count();
+
+        auto const targetModel = wrapper->CreateModel();
+        auto targetReader = targetModel->QueryReader("3mf");
+        targetReader->SetStrictModeActive(true);
+
+        targetReader->ReadFromFile(InFolder + "template.3mf");
+        auto previousTargetFunctionCount = targetModel->GetFunctions()->Count();
+
+        EXPECT_NO_THROW(targetModel->MergeFromModel(sourceModel.get()));
+
+        auto targetFunctionsIter = targetModel->GetFunctions();
+        EXPECT_EQ(targetFunctionsIter->Count(), sourceModelFunctionCount + previousTargetFunctionCount);
     }
 
 }  // namespace Lib3MF
diff --git a/Tests/TestFiles/Volumetric/template.3mf b/Tests/TestFiles/Volumetric/template.3mf
new file mode 100644
index 000000000..4cd785eba
Binary files /dev/null and b/Tests/TestFiles/Volumetric/template.3mf differ