diff --git a/sysrap/scuda.h b/sysrap/scuda.h
index 762883e4ec..d791a6546c 100644
--- a/sysrap/scuda.h
+++ b/sysrap/scuda.h
@@ -101,6 +101,11 @@ SUTIL_INLINE SUTIL_HOSTDEVICE unsigned long long min(unsigned long long a, unsig
     return a < b ? a : b;
 }
 
+// Avoid conflict with C++20 std::lerp (and <math.h> bringing it into global)
+
+#if defined(__cpp_lib_interpolate) // && !defined(__CUDA_ARCH__)
+using std::lerp;                   // make std::lerp visible to unqualified calls
+#else
 
 /** lerp */
 SUTIL_INLINE SUTIL_HOSTDEVICE float lerp(const float a, const float b, const float t)
@@ -108,8 +113,7 @@ SUTIL_INLINE SUTIL_HOSTDEVICE float lerp(const float a, const float b, const flo
   return a + t*(b-a);
 }
 
-
-
+#endif
 
 /** bilerp */
 SUTIL_INLINE SUTIL_HOSTDEVICE float bilerp(const float x00, const float x10, const float x01, const float x11,
diff --git a/u4/U4SolidMaker.cc b/u4/U4SolidMaker.cc
index c14eec8195..ab589a69c5 100644
--- a/u4/U4SolidMaker.cc
+++ b/u4/U4SolidMaker.cc
@@ -2138,7 +2138,7 @@ const G4VSolid* U4SolidMaker::BltLocalFastenerAcrylicConstruction(const char* na
 {
     [[maybe_unused]] const char* PREFIX = "BltLocalFastenerAcrylicConstruction" ; 
     assert( sstr::StartsWith(name,PREFIX ));
-    long num_column = sstr::ExtractLong(name, 1) ; 
+    const size_t num_column = static_cast<size_t>(sstr::ExtractLong(name, 1));
 
     LOG(info) 
         << " name " <<  ( name ? name : "-" )
@@ -2151,8 +2151,10 @@ const G4VSolid* U4SolidMaker::BltLocalFastenerAcrylicConstruction(const char* na
 
     G4Tubs* screw = new G4Tubs("screw",0,13*mm,50.*mm,0.0*deg,360.0*deg);
 
-    G4ThreeVector tlate[num_column] = {} ; 
-    for(long i=0;i<num_column;i++) tlate[i] = G4ThreeVector(164.*cos(i*pi/4)*mm, 164.*sin(i*pi/4)*mm,-65.0*mm);
+    std::vector<G4ThreeVector> tlate(num_column, G4ThreeVector(0, 0, 0));
+
+    for (long i = 0; i < num_column; i++)
+        tlate[i] = G4ThreeVector(164. * cos(i * pi / 4) * mm, 164. * sin(i * pi / 4) * mm, -65.0 * mm);
 
     G4VSolid* muni = screw ; 
     for(long i=1 ; i < num_column ; i++) muni = new G4UnionSolid( name, muni, screw, 0, tlate[i] ) ;