diff --git a/dali/dfu/dfurun.cpp b/dali/dfu/dfurun.cpp
index 72989b5ed34..36de1b7a9eb 100644
--- a/dali/dfu/dfurun.cpp
+++ b/dali/dfu/dfurun.cpp
@@ -1442,6 +1442,8 @@ class CDFUengine: public CInterface, implements IDFUengine
                 }
                 break;
             }
+
+            bool ensureLfnAlreadyPublished = false;
             // fill dstfile for commands that need it
             switch (cmd) {
             case DFUcmd_copymerge:
@@ -1542,6 +1544,14 @@ class CDFUengine: public CInterface, implements IDFUengine
                                 Owned<IDistributedFile> oldfile = wsdfs::lookup(tmp.str(),userdesc,AccessMode::tbdWrite,false,false,nullptr,defaultPrivilegedUser,INFINITE);
                                 if (oldfile)
                                 {
+                                    if (options->getEnsure())
+                                    {
+                                        // logical file already exists.
+                                        ensureLfnAlreadyPublished = true;
+                                        dstFile.setown(oldfile.getClear());
+                                        dstName.set(tmp);
+                                        break;
+                                    }
                                     StringBuffer reason;
                                     bool canRemove = oldfile->canRemove(reason);
                                     oldfile.clear();
@@ -1700,12 +1710,35 @@ class CDFUengine: public CInterface, implements IDFUengine
                             }
                         }
                         else {
-                            fsys.copy(srcFile,dstFile,recovery, recoveryconn, filter, opttree, &feedback, &abortnotify, dfuwuid);
-                            if (!abortnotify.abortRequested()) {
-                                if (needrep)
-                                    replicating = true;
+                            bool performCopy = true;
+                            if (options->getEnsure())
+                            {
+                                if (ensureLfnAlreadyPublished)
+                                    performCopy = false;
                                 else
-                                    dstFile->attach(dstName.get(),userdesc);
+                                {
+                                    if (dstFile->existsPhysicalPartFiles(0))
+                                    {
+                                        dstFile->attach(dstName.get(), userdesc);
+                                        performCopy = false;
+                                    }
+                                }
+                                if (!performCopy)
+                                {
+                                    feedback.repmode=cProgressReporter::REPnone;
+                                    feedback.displaySummary(nullptr, 0);
+                                    Audit("COPYENSURE", userdesc, srcFile?srcName.str():nullptr, dstName.get());
+                                }
+                            }
+                            if (performCopy)
+                            {
+                                fsys.copy(srcFile,dstFile,recovery, recoveryconn, filter, opttree, &feedback, &abortnotify, dfuwuid);
+                                if (!abortnotify.abortRequested()) {
+                                    if (needrep)
+                                        replicating = true;
+                                    else
+                                        dstFile->attach(dstName.get(),userdesc);
+                                }
                                 Audit("COPY",userdesc,srcFile?srcName.str():NULL,dstName.get());
                             }
                         }
diff --git a/dali/dfu/dfuwu.cpp b/dali/dfu/dfuwu.cpp
index 2444d37fd41..26306e8db90 100644
--- a/dali/dfu/dfuwu.cpp
+++ b/dali/dfu/dfuwu.cpp
@@ -2002,6 +2002,11 @@ class CDFUoptions: public CLinkedDFUWUchild, implements IDFUoptions
         return queryRoot()->getPropInt("@overwrite")!=0;
     }
 
+    bool getEnsure() const
+    {
+        return queryRoot()->getPropInt("@ensure")!=0;
+    }
+
     DFUreplicateMode getReplicateMode(StringBuffer &cluster, bool &repeatlast,bool &onlyrepeated) const
     {
         repeatlast = false;
@@ -2146,7 +2151,7 @@ class CDFUoptions: public CLinkedDFUWUchild, implements IDFUoptions
         queryRoot()->setPropInt("@throttle",val);
     }
 
-    void setTransferBufferSize(unsigned val)
+    void setTransferBufferSize(size32_t val)
     {
         queryRoot()->setPropInt("@transferBufferSize",val);
     }
@@ -2161,6 +2166,11 @@ class CDFUoptions: public CLinkedDFUWUchild, implements IDFUoptions
         queryRoot()->setPropInt("@overwrite",val?1:0);
     }
 
+    void setEnsure(bool val=true)
+    {
+        queryRoot()->setPropInt("@ensure",val?1:0);
+    }
+
     void setReplicateMode(DFUreplicateMode val,const char *cluster=NULL,bool repeatlast=false,bool onlyrepeated=false)
     {
         queryRoot()->setPropInt("@replicatemode",(int)val);
diff --git a/dali/dfu/dfuwu.hpp b/dali/dfu/dfuwu.hpp
index 59c15a49e9d..923630a719c 100644
--- a/dali/dfu/dfuwu.hpp
+++ b/dali/dfu/dfuwu.hpp
@@ -153,6 +153,7 @@ interface IConstDFUoptions : extends IInterface
     virtual size32_t getTransferBufferSize() const = 0;
     virtual bool getVerify() const = 0;
     virtual bool getOverwrite() const = 0;
+    virtual bool getEnsure() const = 0;
     virtual DFUreplicateMode getReplicateMode(StringBuffer &cluster, bool &repeatlast,bool &onlyrepeated) const = 0;
     virtual const char *queryPartFilter() const = 0;
     virtual bool getKeepHeader() const = 0;
@@ -195,6 +196,7 @@ interface IDFUoptions : extends IConstDFUoptions
     virtual void setTransferBufferSize(size32_t val) = 0;
     virtual void setVerify(bool val=true) = 0;
     virtual void setOverwrite(bool val=true) = 0;
+    virtual void setEnsure(bool val=true) = 0;
     virtual void setReplicateMode(DFUreplicateMode val,const char *cluster=NULL,bool repeatlast=false,bool onlyrepeated=false) = 0;
     virtual void setPartFilter(const char *filter) = 0;             // format n,n-n,n etc
     virtual void setKeepHeader(bool val=true) = 0;
diff --git a/esp/scm/ws_fs.ecm b/esp/scm/ws_fs.ecm
index 0243b320fcd..01a57f89f58 100644
--- a/esp/scm/ws_fs.ecm
+++ b/esp/scm/ws_fs.ecm
@@ -481,6 +481,7 @@ ESPrequest [nil_remove] Copy
     string srcusername;
     string srcpassword;
     bool   overwrite;
+    bool   ensure;
     bool   replicate;
     int    ReplicateOffset(1);
 
diff --git a/esp/services/ws_fs/ws_fsService.cpp b/esp/services/ws_fs/ws_fsService.cpp
index 8f93fb9c642..b7fe8b6bcbe 100644
--- a/esp/services/ws_fs/ws_fsService.cpp
+++ b/esp/services/ws_fs/ws_fsService.cpp
@@ -2790,6 +2790,7 @@ bool CFileSprayEx::onCopy(IEspContext &context, IEspCopy &req, IEspCopyResponse
         wuFSpecDest->setLogicalName(dstname);
         wuFSpecDest->setFileMask(fileMask.str());
         wuOptions->setOverwrite(req.getOverwrite());
+        wuOptions->setEnsure(req.getEnsure());
         wuOptions->setPreserveCompression(req.getPreserveCompression());
         if (!req.getExpireDays_isNull())
             wuOptions->setExpireDays(req.getExpireDays());