diff --git a/src/simplebuild_dgcode/data/pkgs/MCPL/G4MCPLPlugins/pymod__MCPLGen/mod.cc b/src/simplebuild_dgcode/data/pkgs/MCPL/G4MCPLPlugins/pymod__MCPLGen/mod.cc
index 671946b..7efc5c6 100644
--- a/src/simplebuild_dgcode/data/pkgs/MCPL/G4MCPLPlugins/pymod__MCPLGen/mod.cc
+++ b/src/simplebuild_dgcode/data/pkgs/MCPL/G4MCPLPlugins/pymod__MCPLGen/mod.cc
@@ -294,11 +294,9 @@ void MCPLGen::init_weight_scale()
     return;//not present (e.g. files from older McStas versions): use weights as stored
   if ( !(nrays > 0.0) || !std::isfinite(nrays) ) {
     if (nrays == -1.0)
-      printf("MCPLGen ERROR - The input file has a stat:sum:initial_ray_count value which is not"
-             " available (for instance due to an interrupted run of the application writing the file,"
-             " or because the file contains only a part of the particles of another file), so the weights"
-             " can not be normalised. Set normalise_by_initial_ray_count=false to use the weights as"
-             " stored in the file.\n");
+      printf("MCPLGen ERROR - The input file has a stat:sum:initial_ray_count value of -1, which"
+             " means that the value is not available, so the weights can not be normalised. Set"
+             " normalise_by_initial_ray_count=false to use the weights as stored in the file.\n");
     else
       printf("MCPLGen ERROR - The input file has an invalid stat:sum:initial_ray_count value (%g),"
              " so the weights can not be normalised. Set normalise_by_initial_ray_count=false to use"
diff --git a/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libinc/ASTNode.icc b/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libinc/ASTNode.icc
index eca8064..f90eaa8 100644
--- a/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libinc/ASTNode.icc
+++ b/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libinc/ASTNode.icc
@@ -81,31 +81,6 @@ namespace ExprParser {
 #endif
   }
 
-  template<class TValue>
-  inline ExprEntityPtr ExprEntity<TValue>::optimisedVersion()
-  {
-    //todo: Can we move this to .cc and make sure implementations don't get copied to clients?
-    if (isConstant()) {
-      if (isConstantValue())
-        return 0;//we are already optimal
-      return makeobj<ExprEntityConstantValue<TValue>>(evaluate());
-    }
-    optimiseChildren();
-    auto p = specialOptimisedVersion();
-    if (p) {
-      for (int i =0; i<100000; ++i) {
-        _ensure_type<TValue>(p);
-        if (i==99999)
-          EXPRPARSER_THROW(LogicError,"non-converging optimisation loop");
-        ExprEntityPtr p_opt = p->optimisedVersion();
-        if (!p_opt)
-          break;
-        p = p_opt;
-      }
-    }
-    return p;
-  }
-
   template<class TValue>
   inline ExprEntityConstantValue<TValue>::ExprEntityConstantValue(TValue val)
     : ExprEntity<TValue>(),
diff --git a/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libsrc/ASTNode.cc b/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libsrc/ASTNode.cc
index bec4a5d..f4b8efe 100644
--- a/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libsrc/ASTNode.cc
+++ b/src/simplebuild_dgcode/data/pkgs/Utils/ExprParser/libsrc/ASTNode.cc
@@ -2,6 +2,30 @@
 
 namespace ExprParser {
 
+  template<class TValue>
+  ExprEntityPtr ExprEntity<TValue>::optimisedVersion()
+  {
+    if (isConstant()) {
+      if (isConstantValue())
+        return 0;//we are already optimal
+      return makeobj<ExprEntityConstantValue<TValue>>(evaluate());
+    }
+    optimiseChildren();
+    auto p = specialOptimisedVersion();
+    if (p) {
+      for (int i =0; i<100000; ++i) {
+        _ensure_type<TValue>(p);
+        if (i==99999)
+          EXPRPARSER_THROW(LogicError,"non-converging optimisation loop");
+        ExprEntityPtr p_opt = p->optimisedVersion();
+        if (!p_opt)
+          break;
+        p = p_opt;
+      }
+    }
+    return p;
+  }
+
   template class ExprEntity<float_type>;
   template class ExprEntity<int_type>;
   template class ExprEntity<str_type>;
diff --git a/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/app_mkfile/main.cc b/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/app_mkfile/main.cc
index f6793af..ea94056 100644
--- a/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/app_mkfile/main.cc
+++ b/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/app_mkfile/main.cc
@@ -4,8 +4,8 @@
 //   sb_g4mcpltests_mkfile FILENAME NPARTICLES WEIGHT INITIAL_RAY_COUNT
 //
 //A value of "none" for INITIAL_RAY_COUNT means that the file does not get a
-//stat:sum:initial_ray_count, while "notfinal" leaves the value at -1 (as when
-//the application writing the file was interrupted).
+//stat:sum:initial_ray_count, while "notfinal" leaves the value at -1 (i.e. not
+//available).
 
 #include "mcpl.h"
 #include <cstdio>
diff --git a/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/scripts/testmcplstatsums.log b/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/scripts/testmcplstatsums.log
index f6e001e..44b22bd 100644
--- a/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/scripts/testmcplstatsums.log
+++ b/src/simplebuild_dgcode/data/pkgs_val/UnitTests/G4MCPLTests/scripts/testmcplstatsums.log
@@ -49,7 +49,7 @@
     Output stat:sum:initial_geant4_weights = 10
 
 ==> File with initial_ray_count which is not finalised
-    MCPLGen ERROR - The input file has a stat:sum:initial_ray_count value which is not available (for instance due to an interrupted run of the application writing the file, or because the file contains only a part of the particles of another file), so the weights can not be normalised. Set normalise_by_initial_ray_count=false to use the weights as stored in the file.
+    MCPLGen ERROR - The input file has a stat:sum:initial_ray_count value of -1, which means that the value is not available, so the weights can not be normalised. Set normalise_by_initial_ray_count=false to use the weights as stored in the file.
     (simulation failed as expected)
 
 ==> File with initial_ray_count which is not finalised, not normalised
@@ -144,5 +144,5 @@
     Output stat:sum:initial_ray_count = <unavailable>
 
 ==> File where initial_ray_count is unavailable
-    MCPLGen ERROR - The input file has a stat:sum:initial_ray_count value which is not available (for instance due to an interrupted run of the application writing the file, or because the file contains only a part of the particles of another file), so the weights can not be normalised. Set normalise_by_initial_ray_count=false to use the weights as stored in the file.
+    MCPLGen ERROR - The input file has a stat:sum:initial_ray_count value of -1, which means that the value is not available, so the weights can not be normalised. Set normalise_by_initial_ray_count=false to use the weights as stored in the file.
     (simulation failed as expected)