diff --git a/InnerDetector/InDetRecEvent/InDetPrepRawData/InDetPrepRawData/SiWidth.h b/InnerDetector/InDetRecEvent/InDetPrepRawData/InDetPrepRawData/SiWidth.h
index 601f8196cd22ac92adc80a3fa64c4ce108f445d8..563e23dfab39c45b091f5d126292919c86cc235f 100755
--- a/InnerDetector/InDetRecEvent/InDetPrepRawData/InDetPrepRawData/SiWidth.h
+++ b/InnerDetector/InDetRecEvent/InDetPrepRawData/InDetPrepRawData/SiWidth.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
 */
 
 ///////////////////////////////////////////////////////////////////
@@ -96,8 +96,9 @@ namespace InDet {
    // Private data:
    ///////////////////////////////////////////////////////////////////
  private:
-   Amg::Vector2D m_colrow;//<col, row>
-   Amg::Vector2D m_phirzWidth;
+   // Need to force proper alignment; otherwise cling gets it wrong.
+   alignas(16) Amg::Vector2D m_colrow;//<col, row>
+   alignas(16) Amg::Vector2D m_phirzWidth;
  };
 
  MsgStream&    operator << (MsgStream& stream,    const SiWidth& prd);