diff --git a/src/libslic3r/Utils.hpp b/src/libslic3r/Utils.hpp
index 06c435809..5cdf75037 100644
--- a/src/libslic3r/Utils.hpp
+++ b/src/libslic3r/Utils.hpp
@@ -64,15 +64,23 @@ extern std::string normalize_utf8_nfc(const char *src);
 // for a short while, so the file may not be movable. Retry while we see recoverable errors.
 extern std::error_code rename_file(const std::string &from, const std::string &to);
 
+enum CopyFileResult {
+	SUCCESS = 0,
+	FAIL_COPY_FILE,
+	FAIL_FILES_DIFFERENT,
+	FAIL_RENAMING,
+	FAIL_CHECK_ORIGIN_NOT_OPENED,
+	FAIL_CHECK_TARGET_NOT_OPENED
+};
 // Copy a file, adjust the access attributes, so that the target is writable.
-int copy_file_inner(const std::string &from, const std::string &to);
+CopyFileResult copy_file_inner(const std::string &from, const std::string &to);
 // Copy file to a temp file first, then rename it to the final file name.
 // If with_check is true, then the content of the copied file is compared to the content
 // of the source file before renaming.
-extern int copy_file(const std::string &from, const std::string &to, const bool with_check = false);
+extern CopyFileResult copy_file(const std::string &from, const std::string &to, const bool with_check = false);
 
-// Compares two files, returns 0 if identical, -1 if different.
-extern int check_copy(const std::string& origin, const std::string& copy);
+// Compares two files if identical.
+extern CopyFileResult check_copy(const std::string& origin, const std::string& copy);
 
 // Ignore system and hidden files, which may be created by the DropBox synchronisation process.
 // https://github.com/prusa3d/PrusaSlicer/issues/1298
diff --git a/src/libslic3r/utils.cpp b/src/libslic3r/utils.cpp
index 104d0c5ff..ad91e5239 100644
--- a/src/libslic3r/utils.cpp
+++ b/src/libslic3r/utils.cpp
@@ -417,7 +417,7 @@ std::error_code rename_file(const std::string &from, const std::string &to)
 #endif
 }
 
-int copy_file_inner(const std::string& from, const std::string& to)
+CopyFileResult copy_file_inner(const std::string& from, const std::string& to)
 {
 	const boost::filesystem::path source(from);
 	const boost::filesystem::path target(to);
@@ -433,40 +433,40 @@ int copy_file_inner(const std::string& from, const std::string& to)
 	boost::filesystem::permissions(target, perms, ec);
 	boost::filesystem::copy_file(source, target, boost::filesystem::copy_option::overwrite_if_exists, ec);
 	if (ec) {
-		return -1;
+		return FAIL_COPY_FILE;
 	}
 	boost::filesystem::permissions(target, perms, ec);
-	return 0;
+	return SUCCESS;
 }
 
-int copy_file(const std::string &from, const std::string &to, const bool with_check)
+CopyFileResult copy_file(const std::string &from, const std::string &to, const bool with_check)
 {
 	std::string to_temp = to + ".tmp";
-	int ret_val = copy_file_inner(from,to_temp);
-    if(ret_val == 0)
+	CopyFileResult ret_val = copy_file_inner(from,to_temp);
+    if(ret_val == SUCCESS)
 	{
         if (with_check)
             ret_val = check_copy(from, to_temp);
 
         if (ret_val == 0 && rename_file(to_temp, to))
-        	ret_val = -3;
+        	ret_val = FAIL_RENAMING;
 	}
 	return ret_val;
 }
 
-int check_copy(const std::string &origin, const std::string &copy)
+CopyFileResult check_copy(const std::string &origin, const std::string &copy)
 {
 	boost::nowide::ifstream f1(origin, std::ifstream::in | std::ifstream::binary | std::ifstream::ate);
 	boost::nowide::ifstream f2(copy, std::ifstream::in | std::ifstream::binary | std::ifstream::ate);
 
 	if (f1.fail())
-		return -4;
+		return FAIL_CHECK_ORIGIN_NOT_OPENED;
 	if (f2.fail())
-		return -5;
+		return FAIL_CHECK_TARGET_NOT_OPENED;
 
 	std::streampos fsize = f1.tellg();
 	if (fsize != f2.tellg())
-		return -2;
+		return FAIL_FILES_DIFFERENT;
 
 	f1.seekg(0, std::ifstream::beg);
 	f2.seekg(0, std::ifstream::beg);
@@ -483,12 +483,12 @@ int check_copy(const std::string &origin, const std::string &copy)
 		if (origin_cnt != copy_cnt ||
 			(origin_cnt > 0 && std::memcmp(buffer_origin.data(), buffer_copy.data(), origin_cnt) != 0))
 			// Files are different.
-			return -2;
+			return FAIL_FILES_DIFFERENT;
 		fsize -= origin_cnt;
     } while (f1.good() && f2.good());
 
     // All data has been read and compared equal.
-    return (f1.eof() && f2.eof() && fsize == 0) ? 0 : -2;
+    return (f1.eof() && f2.eof() && fsize == 0) ? SUCCESS : FAIL_FILES_DIFFERENT;
 }
 
 // Ignore system and hidden files, which may be created by the DropBox synchronisation process.
diff --git a/src/slic3r/GUI/BackgroundSlicingProcess.cpp b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
index c4e6272ba..c3cbba395 100644
--- a/src/slic3r/GUI/BackgroundSlicingProcess.cpp
+++ b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
@@ -104,21 +104,24 @@ void BackgroundSlicingProcess::process_fff()
 			bool with_check = GUI::RemovableDriveManager::get_instance().is_path_on_removable_drive(export_path);
 			int copy_ret_val = copy_file(m_temp_output_path, export_path, with_check);
 			switch (copy_ret_val){
-			case 0: break; // no error
-			case -2: 
+			case SUCCESS: break; // no error
+			case FAIL_COPY_FILE:
+				throw std::runtime_error(_utf8(L("Copying of the temporary G-code to the output G-code failed. Maybe the SD card is write locked?")));
+				break;
+			case FAIL_FILES_DIFFERENT: 
 				throw std::runtime_error((boost::format(_utf8(L("Copying of the temporary G-code to the output G-code failed. There might be problem with target device, please try exporting again or using different device. The corrupted output G-code is at %1%.tmp."))) % export_path).str());
 				break;
-			case -3: 
+			case FAIL_RENAMING: 
 				throw std::runtime_error((boost::format(_utf8(L("Renaming of the G-code after copying to the selected destination folder has failed. Current path is %1%.tmp. Please try exporting again."))) % export_path).str()); 
 				break;
-			case -4: 
+			case FAIL_CHECK_ORIGIN_NOT_OPENED: 
 				throw std::runtime_error((boost::format(_utf8(L("Copying of the temporary G-code has finished but the original code at %1% couldn't be opened during copy check. The output G-code is at %2%.tmp."))) % m_temp_output_path % export_path).str());
 				break;
-			case -5: 
+			case FAIL_CHECK_TARGET_NOT_OPENED: 
 				throw std::runtime_error((boost::format(_utf8(L("Copying of the temporary G-code has finished but the exported code couldn't be opened during copy check. The output G-code is at %1%.tmp."))) % export_path).str()); 
 				break;
 			default:
-				throw std::runtime_error(_utf8(L("Copying of the temporary G-code to the output G-code failed. Maybe the SD card is write locked?"))); 
+				BOOST_LOG_TRIVIAL(warning) << "Unexpected fail code(" << (int)copy_ret_val << ") durring copy_file() to " << export_path << ".";
 				break;
 			}
 			
@@ -473,7 +476,7 @@ void BackgroundSlicingProcess::prepare_upload()
 
 	if (m_print == m_fff_print) {
 		m_print->set_status(95, _utf8(L("Running post-processing scripts")));
-		if (copy_file(m_temp_output_path, source_path.string()) != 0) {
+		if (copy_file(m_temp_output_path, source_path.string()) != SUCCESS) {
 			throw std::runtime_error(_utf8(L("Copying of the temporary G-code to the output G-code failed")));
 		}
 		run_post_process_scripts(source_path.string(), m_fff_print->config());