diff --git a/src/basicio.cpp b/src/basicio.cpp
index cd28806513..15d0bf7534 100644
--- a/src/basicio.cpp
+++ b/src/basicio.cpp
@@ -1420,7 +1420,7 @@ int64_t HttpIo::HttpImpl::getFileLength() {
   request["verb"] = "HEAD";
   int serverCode = http(request, response, errors);
   if (serverCode < 0 || serverCode >= 400 || !errors.empty()) {
-    throw Error(ErrorCode::kerFileOpenFailed, "http", Exiv2::Internal::stringFormat("%d", serverCode), hostInfo_.Path);
+    throw Error(ErrorCode::kerFileOpenFailed, "http", serverCode, hostInfo_.Path);
   }
 
   auto lengthIter = response.find("Content-Length");
@@ -1444,7 +1444,7 @@ void HttpIo::HttpImpl::getDataByRange(size_t lowBlock, size_t highBlock, std::st
 
   int serverCode = http(request, responseDic, errors);
   if (serverCode < 0 || serverCode >= 400 || !errors.empty()) {
-    throw Error(ErrorCode::kerFileOpenFailed, "http", Exiv2::Internal::stringFormat("%d", serverCode), hostInfo_.Path);
+    throw Error(ErrorCode::kerFileOpenFailed, "http", serverCode, hostInfo_.Path);
   }
   response = responseDic["body"];
 }
@@ -1497,7 +1497,7 @@ void HttpIo::HttpImpl::writeRemote(const byte* data, size_t size, size_t from, s
 
   int serverCode = http(request, response, errors);
   if (serverCode < 0 || serverCode >= 400 || !errors.empty()) {
-    throw Error(ErrorCode::kerFileOpenFailed, "http", Exiv2::Internal::stringFormat("%d", serverCode), hostInfo_.Path);
+    throw Error(ErrorCode::kerFileOpenFailed, "http", serverCode, hostInfo_.Path);
   }
 }
 
@@ -1594,7 +1594,7 @@ int64_t CurlIo::CurlImpl::getFileLength() {
   int serverCode;
   curl_easy_getinfo(curl_, CURLINFO_RESPONSE_CODE, &serverCode);  // get code
   if (serverCode >= 400 || serverCode < 0) {
-    throw Error(ErrorCode::kerFileOpenFailed, "http", Exiv2::Internal::stringFormat("%d", serverCode), path_);
+    throw Error(ErrorCode::kerFileOpenFailed, "http", serverCode, path_);
   }
   // get length
   curl_off_t temp;
@@ -1628,7 +1628,7 @@ void CurlIo::CurlImpl::getDataByRange(size_t lowBlock, size_t highBlock, std::st
   int serverCode;
   curl_easy_getinfo(curl_, CURLINFO_RESPONSE_CODE, &serverCode);  // get code
   if (serverCode >= 400 || serverCode < 0) {
-    throw Error(ErrorCode::kerFileOpenFailed, "http", Exiv2::Internal::stringFormat("%d", serverCode), path_);
+    throw Error(ErrorCode::kerFileOpenFailed, "http", serverCode, path_);
   }
 }
 
@@ -1676,7 +1676,7 @@ void CurlIo::CurlImpl::writeRemote(const byte* data, size_t size, size_t from, s
   int serverCode;
   curl_easy_getinfo(curl_, CURLINFO_RESPONSE_CODE, &serverCode);
   if (serverCode >= 400 || serverCode < 0) {
-    throw Error(ErrorCode::kerFileOpenFailed, "http", Exiv2::Internal::stringFormat("%d", serverCode), path_);
+    throw Error(ErrorCode::kerFileOpenFailed, "http", serverCode, path_);
   }
 }
 
diff --git a/src/rafimage.cpp b/src/rafimage.cpp
index 72cc2845aa..495e96920b 100644
--- a/src/rafimage.cpp
+++ b/src/rafimage.cpp
@@ -71,11 +71,11 @@ void RafImage::printStructure(std::ostream& out, PrintStructureOption option, si
   if (bPrint) {
     io_->seek(0, BasicIo::beg);  // rewind
     size_t address = io_->tell();
-    const auto format = " %8zu | %8ld | ";
+    constexpr auto format = " %8zu | %8ld | ";
 
     {
       out << Internal::indent(depth) << "STRUCTURE OF RAF FILE: " << io().path() << std::endl;
-      out << Internal::indent(depth) << Internal::stringFormat("  Address |   Length | Payload") << std::endl;
+      out << Internal::indent(depth) << "  Address |   Length | Payload" << std::endl;
     }
 
     byte magicdata[17];
diff --git a/src/webpimage.cpp b/src/webpimage.cpp
index 1265731431..f8d0f463ee 100644
--- a/src/webpimage.cpp
+++ b/src/webpimage.cpp
@@ -419,7 +419,7 @@ void WebPImage::printStructure(std::ostream& out, PrintStructureOption option, s
 
     if (bPrint) {
       out << Internal::indent(depth) << "STRUCTURE OF WEBP FILE: " << io().path() << std::endl;
-      out << Internal::indent(depth) << Internal::stringFormat(" Chunk |   Length |   Offset | Payload") << std::endl;
+      out << Internal::indent(depth) << " Chunk |   Length |   Offset | Payload" << std::endl;
     }
 
     io_->seek(0, BasicIo::beg);  // rewind