diff --git a/DetectorDescription/GeoPrimitives/GeoPrimitives/GeoPrimitivesDict.h b/DetectorDescription/GeoPrimitives/GeoPrimitives/GeoPrimitivesDict.h
index e1d616e81f3c0b8229670fb27667365740a53687..fefc3d8d6fabeeccaf28354ce6ceb3607767ad1a 100644
--- a/DetectorDescription/GeoPrimitives/GeoPrimitives/GeoPrimitivesDict.h
+++ b/DetectorDescription/GeoPrimitives/GeoPrimitives/GeoPrimitivesDict.h
@@ -23,10 +23,12 @@ struct GeoPrimitivesInstan
   Eigen::MatrixBase<Eigen::Matrix<double,3,1,0,3,1> > m_vb3;
   Eigen::MatrixBase<Eigen::Matrix<double,5,1,0,5,1> > m_vb5;
   Eigen::DenseBase<Eigen::Block<const Eigen::Matrix<double,4,4,0,4,4>,3,1,false> > m_db4;
+#if ! EIGEN_VERSION_AT_LEAST( 3, 3, 0 )
   Eigen::internal::special_scalar_op_base<Eigen::Block<const Eigen::Matrix<double,4,4,0,4,4>,3,1,false>,double,double,Eigen::DenseBase<Eigen::Block<const Eigen::Matrix<double,4,4,0,4,4>,3,1,false> >,false> m_ss4;
   Eigen::internal::special_scalar_op_base<Eigen::Matrix<double,2,1,0,2,1>,double,double,Eigen::MatrixBase<Eigen::Matrix<double,2,1,0,2,1> >,false> m_ssv2;
   Eigen::internal::special_scalar_op_base<Eigen::Matrix<double,3,1,0,3,1>,double,double,Eigen::MatrixBase<Eigen::Matrix<double,3,1,0,3,1> >,false> m_ssv3;
   Eigen::internal::special_scalar_op_base<Eigen::Matrix<double,5,1,0,5,1>,double,double,Eigen::MatrixBase<Eigen::Matrix<double,5,1,0,5,1> >,false> m_ssv5;
+#endif // EIGEN_VERSION_AT_LEAST
   Eigen::DenseCoeffsBase<Eigen::Block<const Eigen::Matrix<double,4,4,0,4,4>,3,1,false>,2> m_dc4_2;
   Eigen::DenseCoeffsBase<Eigen::Block<const Eigen::Matrix<double,4,4,0,4,4>,3,1,false>,0> m_dc4_0;
   Eigen::PlainObjectBase<Eigen::Matrix<double,3,3,0,3,3> > m_pm3;
diff --git a/ForwardDetectors/AFP/AFP_Reconstruction/AFP_LocReco/AFP_LocReco/AFP_SIDBasicKalman.h b/ForwardDetectors/AFP/AFP_Reconstruction/AFP_LocReco/AFP_LocReco/AFP_SIDBasicKalman.h
index aaedfc244a857e426ee6ff13c6bf4ef0957fc0d8..f707ddc873134487d6319f89b81515ff96f7a8a3 100644
--- a/ForwardDetectors/AFP/AFP_Reconstruction/AFP_LocReco/AFP_LocReco/AFP_SIDBasicKalman.h
+++ b/ForwardDetectors/AFP/AFP_Reconstruction/AFP_LocReco/AFP_LocReco/AFP_SIDBasicKalman.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef AFP_SIDBASICKALMAN_H
@@ -14,7 +14,6 @@
 #include "GaudiKernel/StatusCode.h"
 #include "AthenaKernel/getMessageSvc.h"
 
-#include "Ttypes.h"
 #include "TH2.h"
 #include "TFile.h"
 #include "TMath.h"
diff --git a/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_CenterGravity.h b/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_CenterGravity.h
index 0747ae7ddf95eda8c19262b2e41cb88fd5e4d339..d75ddde3b35604bd93c313104bd629ab537ea679 100644
--- a/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_CenterGravity.h
+++ b/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_CenterGravity.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef ALFA_CENTERGRAVITY_H
@@ -12,12 +12,10 @@
 #include "AthenaKernel/MsgStreamMember.h"
 #include "AthenaBaseComps/AthMsgStreamMacros.h"
 
-//#include "GaudiKernel/MsgStream.h"
 #include "GaudiKernel/StatusCode.h"
 
 #include "AthenaKernel/getMessageSvc.h"
 
-#include "Ttypes.h"
 #include "TH1.h"
 #include "TH2.h"
 
diff --git a/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_MDOverlap.h b/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_MDOverlap.h
index 94b32de3f4c2e13e362b3e4cb60ab496eb9555c9..edb07b0a72949afcca7d747366b0bcfbf059ee0f 100644
--- a/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_MDOverlap.h
+++ b/ForwardDetectors/ALFA/ALFA_Reconstruction/ALFA_LocRec/ALFA_LocRec/ALFA_MDOverlap.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef ALFA_MDOVERLAP_H
@@ -12,12 +12,10 @@
 #include "AthenaKernel/MsgStreamMember.h"
 #include "AthenaBaseComps/AthMsgStreamMacros.h"
 
-//#include "GaudiKernel/MsgStream.h"
 #include "GaudiKernel/StatusCode.h"
 
 #include "AthenaKernel/getMessageSvc.h"
 
-#include "Ttypes.h"
 #include "TH1.h"
 #include "TH2.h"
 
diff --git a/Simulation/G4Utilities/G4UserActions/src/components/G4UserActions_entries.cxx b/Simulation/G4Utilities/G4UserActions/src/components/G4UserActions_entries.cxx
index 20927db73188ab9417076fc7ebbdafafaced6e65..b8533db41f8bb7726ea106ce01ce13b7b6a1846f 100644
--- a/Simulation/G4Utilities/G4UserActions/src/components/G4UserActions_entries.cxx
+++ b/Simulation/G4Utilities/G4UserActions/src/components/G4UserActions_entries.cxx
@@ -1,6 +1,11 @@
 #include "G4UserActions/G4SimTimerTool.h"
 #include "G4UserActions/G4TrackCounterTool.h"
 #include "G4UserActions/LooperKillerTool.h"
+// This is a weird one... Geant4 declares 'times' as 'otimes' in some of its
+// headers. That can have a catastrophic interference with how Boost uses the
+// `times` variable itself. This next line just gets rid of one such
+// catastrophic interference. Though this is super fragile...
+#undef times
 #include "G4UserActions/CosmicPerigeeActionTool.h"
 #include "G4UserActions/MomentumConservationTool.h"
 #include "G4UserActions/FastIDKillerTool.h"
diff --git a/Trigger/TrigConfiguration/TrigConfDBConnection/CMakeLists.txt b/Trigger/TrigConfiguration/TrigConfDBConnection/CMakeLists.txt
index eb815e2d6332dac2ae8e305a820cf90dcb4ba1c4..f4b502b360cc590d01e56d43a502aed3339ef604 100644
--- a/Trigger/TrigConfiguration/TrigConfDBConnection/CMakeLists.txt
+++ b/Trigger/TrigConfiguration/TrigConfDBConnection/CMakeLists.txt
@@ -6,7 +6,8 @@
 atlas_subdir( TrigConfDBConnection )
 
 # External dependencies:
-find_package( Boost COMPONENTS filesystem thread system python )
+find_package( Boost COMPONENTS filesystem thread system
+   OPTIONAL_COMPONENTS python python27 )
 find_package( Frontier_Client )
 find_package( PythonLibs )