diff --git a/include/api/CBoostedTreeInferenceModelBuilder.h b/include/api/CBoostedTreeInferenceModelBuilder.h
index 6cd1680836..cfb124c9f7 100644
--- a/include/api/CBoostedTreeInferenceModelBuilder.h
+++ b/include/api/CBoostedTreeInferenceModelBuilder.h
@@ -14,6 +14,8 @@
 
 #include <rapidjson/document.h>
 
+#include <boost/unordered_map.hpp>
+
 #include <string>
 
 namespace ml {
@@ -25,7 +27,7 @@ class API_EXPORT CBoostedTreeInferenceModelBuilder : public maths::CBoostedTree:
     using TDoubleVec = std::vector<double>;
     using TStrVec = std::vector<std::string>;
     using TStrVecVec = std::vector<TStrVec>;
-    using TSizeStringUMap = std::unordered_map<std::size_t, std::string>;
+    using TSizeStringUMap = boost::unordered_map<std::size_t, std::string>;
     using TSizeStringUMapVec = std::vector<TSizeStringUMap>;
     using TVector = maths::CBoostedTreeNode::TVector;
     using TApiCustomEncodingUPtr = std::unique_ptr<api::CCustomEncoding>;
@@ -59,8 +61,8 @@ class API_EXPORT CBoostedTreeInferenceModelBuilder : public maths::CBoostedTree:
 
 private:
     using TOneHotEncodingUPtr = std::unique_ptr<COneHotEncoding>;
-    using TOneHotEncodingUMap = std::unordered_map<std::string, TOneHotEncodingUPtr>;
-    using TStringDoubleUMap = std::unordered_map<std::string, double>;
+    using TOneHotEncodingUMap = boost::unordered_map<std::string, TOneHotEncodingUPtr>;
+    using TStringDoubleUMap = boost::unordered_map<std::string, double>;
 
 private:
     virtual void setTargetType() = 0;
diff --git a/include/api/CDataFrameAnalysisInstrumentation.h b/include/api/CDataFrameAnalysisInstrumentation.h
index bcfdef69aa..e5c7fefd22 100644
--- a/include/api/CDataFrameAnalysisInstrumentation.h
+++ b/include/api/CDataFrameAnalysisInstrumentation.h
@@ -21,7 +21,6 @@
 #include <cstdint>
 #include <memory>
 #include <mutex>
-#include <unordered_map>
 
 namespace ml {
 namespace api {
diff --git a/include/api/CInferenceModelDefinition.h b/include/api/CInferenceModelDefinition.h
index d4d7fa411b..4281fac397 100644
--- a/include/api/CInferenceModelDefinition.h
+++ b/include/api/CInferenceModelDefinition.h
@@ -16,10 +16,10 @@
 #include <rapidjson/ostreamwrapper.h>
 
 #include <boost/optional.hpp>
+#include <boost/unordered_map.hpp>
 
 #include <sstream>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 namespace ml {
@@ -354,7 +354,7 @@ class API_EXPORT CFrequencyEncoding final : public CEncoding {
     private:
         const CFrequencyEncoding& m_Encoding;
     };
-    using TStringDoubleUMap = const std::unordered_map<std::string, double>;
+    using TStringDoubleUMap = const boost::unordered_map<std::string, double>;
 
 public:
     ~CFrequencyEncoding() override = default;
@@ -417,7 +417,7 @@ class API_EXPORT CTargetMeanEncoding final : public CEncoding {
     private:
         const CTargetMeanEncoding& m_Encoding;
     };
-    using TStringDoubleUMap = std::unordered_map<std::string, double>;
+    using TStringDoubleUMap = boost::unordered_map<std::string, double>;
 
 public:
     ~CTargetMeanEncoding() override = default;
@@ -462,9 +462,9 @@ class API_EXPORT CInferenceModelDefinition : public CSerializableToJsonStream {
     using TApiCustomEncodingUPtr = std::unique_ptr<api::CCustomEncoding>;
     using TApiCustomEncodingUPtrVec = std::vector<TApiCustomEncodingUPtr>;
     using TRapidJsonWriter = core::CRapidJsonConcurrentLineWriter;
-    using TSizeStringUMap = std::unordered_map<std::size_t, std::string>;
+    using TSizeStringUMap = boost::unordered_map<std::size_t, std::string>;
     using TSizeStringUMapVec = std::vector<TSizeStringUMap>;
-    using TStringSizeUMap = std::unordered_map<std::string, std::size_t>;
+    using TStringSizeUMap = boost::unordered_map<std::string, std::size_t>;
     using TStringSizeUMapVec = std::vector<TStringSizeUMap>;
     using TStringVec = std::vector<std::string>;
     using TTrainedModelUPtr = CEnsemble::TTrainedModelUPtr;
diff --git a/include/api/CInferenceModelMetadata.h b/include/api/CInferenceModelMetadata.h
index 423e8ada69..2539d5db89 100644
--- a/include/api/CInferenceModelMetadata.h
+++ b/include/api/CInferenceModelMetadata.h
@@ -13,6 +13,8 @@
 #include <api/CInferenceModelDefinition.h>
 #include <api/ImportExport.h>
 
+#include <boost/unordered_map.hpp>
+
 #include <string>
 #include <tuple>
 
@@ -83,8 +85,8 @@ class API_EXPORT CInferenceModelMetadata {
     using TMeanAccumulator =
         std::vector<maths::CBasicStatistics::SSampleMean<double>::TAccumulator>;
     using TMinMaxAccumulator = std::vector<maths::CBasicStatistics::CMinMax<double>>;
-    using TSizeMeanAccumulatorUMap = std::unordered_map<std::size_t, TMeanAccumulator>;
-    using TSizeMinMaxAccumulatorUMap = std::unordered_map<std::size_t, TMinMaxAccumulator>;
+    using TSizeMeanAccumulatorUMap = boost::unordered_map<std::size_t, TMeanAccumulator>;
+    using TSizeMinMaxAccumulatorUMap = boost::unordered_map<std::size_t, TMinMaxAccumulator>;
     using TOptionalVector = boost::optional<TVector>;
     using THyperparametersVec = std::vector<SHyperparameterImportance>;
 
diff --git a/lib/api/CInferenceModelDefinition.cc b/lib/api/CInferenceModelDefinition.cc
index 2eaa20c1c1..c34be7f1ca 100644
--- a/lib/api/CInferenceModelDefinition.cc
+++ b/lib/api/CInferenceModelDefinition.cc
@@ -12,13 +12,13 @@
 
 #include <boost/iostreams/filter/gzip.hpp>
 #include <boost/iostreams/filtering_stream.hpp>
+#include <boost/unordered_map.hpp>
+#include <boost/unordered_set.hpp>
 
 #include <cmath>
 #include <iterator>
 #include <memory>
 #include <ostream>
-#include <unordered_map>
-#include <unordered_set>
 
 namespace ml {
 namespace api {
@@ -280,7 +280,7 @@ void CEnsemble::targetType(ETargetType targetType) {
 }
 
 CTrainedModel::TStringVec CEnsemble::removeUnusedFeatures() {
-    std::unordered_set<std::string> set;
+    boost::unordered_set<std::string> set;
     for (auto& trainedModel : this->trainedModels()) {
         TStringVec vec(trainedModel->removeUnusedFeatures());
         set.insert(vec.begin(), vec.end());
@@ -380,7 +380,7 @@ CTree::TTreeNodeVec& CTree::treeStructure() {
 }
 
 CTrainedModel::TStringVec CTree::removeUnusedFeatures() {
-    std::unordered_map<std::size_t, std::size_t> selectedFeatureIndices;
+    boost::unordered_map<std::size_t, std::size_t> selectedFeatureIndices;
     for (auto& treeNode : m_TreeStructure) {
         if (treeNode.leaf() == false) {
             std::size_t adjustedIndex{selectedFeatureIndices
diff --git a/lib/model/unittest/CEventRatePopulationModelTest.cc b/lib/model/unittest/CEventRatePopulationModelTest.cc
index 1961423319..c7a510ab19 100644
--- a/lib/model/unittest/CEventRatePopulationModelTest.cc
+++ b/lib/model/unittest/CEventRatePopulationModelTest.cc
@@ -39,13 +39,13 @@
 #include <boost/test/unit_test.hpp>
 #include <boost/tuple/tuple.hpp>
 #include <boost/tuple/tuple_comparison.hpp>
+#include <boost/unordered_map.hpp>
 
 #include <algorithm>
 #include <cstddef>
 #include <map>
 #include <set>
 #include <string>
-#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -279,7 +279,7 @@ BOOST_FIXTURE_TEST_CASE(testFeatures, CTestFixture) {
         }
 
     private:
-        using TDoubleSizeUMap = std::unordered_map<double, std::size_t>;
+        using TDoubleSizeUMap = boost::unordered_map<double, std::size_t>;
 
     private:
         TDoubleSizeUMap m_Uniques;
@@ -287,7 +287,7 @@ BOOST_FIXTURE_TEST_CASE(testFeatures, CTestFixture) {
         TDouble2VecWeightsAryVec m_TrendWeights;
         TDouble2VecWeightsAryVec m_ResidualWeights;
     };
-    using TSizeUniqueValuesUMap = std::unordered_map<std::size_t, CUniqueValues>;
+    using TSizeUniqueValuesUMap = boost::unordered_map<std::size_t, CUniqueValues>;
 
     core_t::TTime startTime = 1367280000;
     const core_t::TTime bucketLength = 3600;