diff --git a/src/colvar/PathMSDBase.cpp b/src/colvar/PathMSDBase.cpp
index 7daf8a429536a5d18a68eeab7cc01b07af134135..9d16ea02533ea63bfc9fdd361e77b5398477010e 100644
--- a/src/colvar/PathMSDBase.cpp
+++ b/src/colvar/PathMSDBase.cpp
@@ -87,7 +87,7 @@ PathMSDBase::PathMSDBase(const ActionOptions&ao):
         if(nat!=mypdb.getAtomNumbers().size()) error("frames should have the same number of atoms");
         if(aaa.empty()) {
           aaa=mypdb.getAtomNumbers();
-          log.printf("  found %d atoms in input \n",aaa.size());
+          log.printf("  found %z atoms in input \n",aaa.size());
           log.printf("  with indices : ");
           for(unsigned i=0; i<aaa.size(); ++i) {
             if(i%25==0) log<<"\n";
diff --git a/src/generic/FitToTemplate.cpp b/src/generic/FitToTemplate.cpp
index 215918b66091bd687e3b6b3cf57ad1603e7422cc..69f0beb28fd4ab5457a9d57ea041579acf17a32b 100644
--- a/src/generic/FitToTemplate.cpp
+++ b/src/generic/FitToTemplate.cpp
@@ -235,7 +235,7 @@ FitToTemplate::FitToTemplate(const ActionOptions&ao):
     error("missing input file " + reference );
 
   requestAtoms(pdb.getAtomNumbers());
-  log.printf("  found %d atoms in input \n",pdb.getAtomNumbers().size());
+  log.printf("  found %z atoms in input \n",pdb.getAtomNumbers().size());
   log.printf("  with indices : ");
   for(unsigned i=0; i<pdb.getAtomNumbers().size(); ++i) {
     if(i%25==0) log<<"\n";
diff --git a/src/mapping/Mapping.cpp b/src/mapping/Mapping.cpp
index 10c6b3d1dcba823f3d13a85b408191031e83c6b6..e132857b805280fd6972775f41a0454a421f4891 100644
--- a/src/mapping/Mapping.cpp
+++ b/src/mapping/Mapping.cpp
@@ -109,7 +109,7 @@ Mapping::Mapping(const ActionOptions&ao):
   if( req_args.size()>0 && atoms.size()>0 ) error("cannot mix atoms and arguments");
   if( req_args.size()>0 ) requestArguments( req_args );
   if( atoms.size()>0 ) {
-    log.printf("  found %d atoms in input \n",atoms.size());
+    log.printf("  found %z atoms in input \n",atoms.size());
     log.printf("  with indices : ");
     for(unsigned i=0; i<atoms.size(); ++i) {
       if(i%25==0) log<<"\n";
diff --git a/src/mapping/PCAVars.cpp b/src/mapping/PCAVars.cpp
index 3f296100ea9b53100a0d2d29431f1afc93ab1b51..d0a0ad7773e5723320c2369fda73754d386a3b57 100644
--- a/src/mapping/PCAVars.cpp
+++ b/src/mapping/PCAVars.cpp
@@ -271,7 +271,7 @@ PCAVars::PCAVars(const ActionOptions& ao):
   std::vector<AtomNumber> atoms; myref->getAtomRequests( atoms, false );
   std::vector<std::string> args; myref->getArgumentRequests( args, false );
   if( atoms.size()>0 ) {
-    log.printf("  found %d atoms in input \n",atoms.size());
+    log.printf("  found %z atoms in input \n",atoms.size());
     log.printf("  with indices : ");
     for(unsigned i=0; i<atoms.size(); ++i) {
       if(i%25==0) log<<"\n";