diff --git a/code/ryzom/tools/patch_gen/patch_gen_common.cpp b/code/ryzom/tools/patch_gen/patch_gen_common.cpp
index c1290cfd5..8ba0d4c5e 100644
--- a/code/ryzom/tools/patch_gen/patch_gen_common.cpp
+++ b/code/ryzom/tools/patch_gen/patch_gen_common.cpp
@@ -49,28 +49,34 @@ void normalisePackageDescriptionFileName(std::string& fileName)
 
 void GeneratePatch(const std::string& srcFileName,const std::string& destFileName,const std::string& patchFileName)
 {
-	std::string cmd="xdelta delta";
-	cmd+=" "+srcFileName+" "+destFileName+" "+patchFileName;
-	nlinfo("executing system command: %s",cmd.c_str());
+	std::string cmd = toString("xdelta delta %s %s %s", srcFileName.c_str(), destFileName.c_str(), patchFileName.c_str());
+
+	nlinfo("Executing system command: %s", cmd.c_str());
+
 #ifdef NL_OS_WINDOWS
-	_spawnlp(_P_WAIT, "xdelta.exe","xdelta.exe","delta",srcFileName.c_str(),destFileName.c_str(),patchFileName.c_str(),NULL);
+	_spawnlp(_P_WAIT, "xdelta.exe", "xdelta.exe", "delta", srcFileName.c_str(), destFileName.c_str(), patchFileName.c_str(), NULL);
 #else // NL_OS_WINDOWS
+	// xdelta-1.x behaves like "diff" and returns 0 for identical files, 1 for different files, 2 for errors
 	sint error = system (cmd.c_str());
-	if (error)
+
+	if (error == 2)
 		nlwarning("'%s' failed with error code %d", cmd.c_str(), error);
 #endif // NL_OS_WINDOWS
 }
 
 void ApplyPatch(const std::string& srcFileName,const std::string& destFileName,const std::string& patchFileName=std::string())
 {
-	std::string cmd="xdelta patch";
-	cmd+=" "+patchFileName+" "+srcFileName+" "+destFileName;
-	nlinfo("executing system command: %s",cmd.c_str());
+	std::string cmd = toString("xdelta patch %s %s %s", patchFileName.c_str(), srcFileName.c_str(), destFileName.c_str());
+
+	nlinfo("Executing system command: %s", cmd.c_str());
+
 #ifdef NL_OS_WINDOWS
-	_spawnlp(_P_WAIT, "xdelta.exe","xdelta.exe","patch",patchFileName.c_str(),srcFileName.c_str(),destFileName.c_str(),NULL);
+	_spawnlp(_P_WAIT, "xdelta.exe", "xdelta.exe", "patch",patchFileName.c_str(), srcFileName.c_str(), destFileName.c_str(), NULL);
 #else // NL_OS_WINDOWS
+	// xdelta-1.x behaves like "diff" and returns 0 for identical files, 1 for different files, 2 for errors
 	sint error = system (cmd.c_str());
-	if (error)
+
+	if (error == 2)
 		nlwarning("'%s' failed with error code %d", cmd.c_str(), error);
 #endif // NL_OS_WINDOWS
 }