diff --git a/application/argumentparser.cpp b/application/argumentparser.cpp
index e5ebe9a..1372b84 100644
--- a/application/argumentparser.cpp
+++ b/application/argumentparser.cpp
@@ -4,6 +4,7 @@
 #include "./failure.h"
 
 #include "../conversion/stringconversion.h"
+#include "../conversion/stringbuilder.h"
 #include "../io/path.h"
 #include "../io/ansiescapecodes.h"
 
@@ -250,7 +251,7 @@ void ArgumentReader::read(ArgumentVector &args)
                         ++index, ++argv, argDenotation = nullptr;
                         break;
                     case UnknownArgumentBehavior::Fail:
-                        throw Failure("The specified argument \"" + string(*argv) + "\" is unknown and will be ignored.");
+                        throw Failure("The specified argument \"" % string(*argv) + "\" is unknown and will be ignored.");
                     }
                 }
             } // if(!matchingArg)
@@ -1122,10 +1123,10 @@ void ArgumentParser::checkConstraints(const ArgumentVector &args)
     for(const Argument *arg : args) {
         const auto occurrences = arg->occurrences();
         if(arg->isParentPresent() && occurrences > arg->maxOccurrences()) {
-            throw Failure("The argument \"" + string(arg->name()) + "\" mustn't be specified more than " + numberToString(arg->maxOccurrences()) + (arg->maxOccurrences() == 1 ? " time." : " times."));
+            throw Failure("The argument \"" % string(arg->name()) % "\" mustn't be specified more than " % numberToString(arg->maxOccurrences()) + (arg->maxOccurrences() == 1 ? " time." : " times."));
         }
         if(arg->isParentPresent() && occurrences < arg->minOccurrences()) {
-            throw Failure("The argument \"" + string(arg->name()) + "\" must be specified at least " + numberToString(arg->minOccurrences()) + (arg->minOccurrences() == 1 ? " time." : " times."));
+            throw Failure("The argument \"" % string(arg->name()) % "\" must be specified at least " % numberToString(arg->minOccurrences()) + (arg->minOccurrences() == 1 ? " time." : " times."));
         }
         Argument *conflictingArgument = nullptr;
         if(arg->isMainArgument()) {
@@ -1136,7 +1137,7 @@ void ArgumentParser::checkConstraints(const ArgumentVector &args)
             conflictingArgument = arg->conflictsWithArgument();
         }
         if(conflictingArgument) {
-            throw Failure("The argument \"" + string(conflictingArgument->name()) + "\" can not be combined with \"" + arg->name() + "\".");
+            throw Failure("The argument \"" % string(conflictingArgument->name()) % "\" can not be combined with \"" + arg->name() + "\".");
         }
         for(size_t i = 0; i != occurrences; ++i) {
             if(!arg->allRequiredValuesPresent(i)) {
diff --git a/chrono/datetime.cpp b/chrono/datetime.cpp
index 67a2d78..2f8f10b 100644
--- a/chrono/datetime.cpp
+++ b/chrono/datetime.cpp
@@ -1,6 +1,7 @@
 #include "./datetime.h"
 
 #include "../conversion/stringconversion.h"
+#include "../conversion/stringbuilder.h"
 
 #include <sstream>
 #include <iomanip>
@@ -168,7 +169,7 @@ std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
         } else if(c == '\0') {
             break;
         } else {
-            throw ConversionException(string("unexpected \"") + c + '\"');
+            throw ConversionException(string("unexpected \"") % c + '\"');
         }
     }
     deltaNegative && (*deltaHourIndex = -*deltaHourIndex);
diff --git a/io/path.cpp b/io/path.cpp
index 15ed782..5ef1484 100644
--- a/io/path.cpp
+++ b/io/path.cpp
@@ -123,10 +123,10 @@ bool settingsDirectory(std::string &result, std::string applicationDirectoryName
         }
 #if defined(PLATFORM_UNIX) || defined(PLATFORM_MAC)
         if(char *homeDir = getenv("HOME")) {
-            result = string(homeDir);
+            result = homeDir;
         } else {
             struct passwd *pw = getpwuid(getuid());
-            result = string(pw->pw_dir);
+            result = pw->pw_dir;
         }
         struct stat sb;
         result += "/.config";
@@ -136,7 +136,8 @@ bool settingsDirectory(std::string &result, std::string applicationDirectoryName
             }
         }
         if(!applicationDirectoryName.empty()) {
-            result += "/" + applicationDirectoryName;
+            result += '/';
+            result += applicationDirectoryName;
             if(createApplicationDirectory && !(stat(result.c_str(), &sb) == 0 && S_ISDIR(sb.st_mode))) {
                 if(mkdir(result.c_str(), S_IRUSR | S_IWUSR | S_IXUSR) != 0) {
                     return false;
@@ -147,7 +148,8 @@ bool settingsDirectory(std::string &result, std::string applicationDirectoryName
         if(char *appData = getenv("appdata")) {
             result = appData;
             if(!applicationDirectoryName.empty()) {
-                result += "\\" + applicationDirectoryName;
+                result += '\\';
+                result += applicationDirectoryName;
                 if(createApplicationDirectory) {
                     // FIXME: use UTF-16 API to support unicode, or rewrite using fs abstraction lib
                     DWORD ftyp = GetFileAttributesA(result.c_str());
diff --git a/tests/argumentparsertests.cpp b/tests/argumentparsertests.cpp
index 793b675..214b5ac 100644
--- a/tests/argumentparsertests.cpp
+++ b/tests/argumentparsertests.cpp
@@ -1,5 +1,7 @@
 #include "./testutils.h"
 
+#include "../conversion/stringbuilder.h"
+
 #include "../application/argumentparser.h"
 #include "../application/argumentparserprivate.h"
 #include "../application/failure.h"
@@ -17,6 +19,7 @@
 
 using namespace std;
 using namespace ApplicationUtilities;
+using namespace ConversionUtilities;
 
 using namespace CPPUNIT_NS;
 
@@ -494,9 +497,9 @@ void ArgumentParserTests::testBashCompletion()
         // order for file names is not specified
         const string res(buffer.str());
         if(res.find(".mkv") < res.find(".ini")) {
-            CPPUNIT_ASSERT_EQUAL("COMPREPLY=('" + mkvFilePath + " '\"'\"'with quote'\"'\"'.mkv' '" + iniFilePath + ".ini' ); compopt -o filenames\n", buffer.str());
+            CPPUNIT_ASSERT_EQUAL("COMPREPLY=('" % mkvFilePath % " '\"'\"'with quote'\"'\"'.mkv' '" % iniFilePath + ".ini' ); compopt -o filenames\n", buffer.str());
         } else {
-            CPPUNIT_ASSERT_EQUAL("COMPREPLY=('" + iniFilePath + ".ini' '" + mkvFilePath + " '\"'\"'with quote'\"'\"'.mkv' ); compopt -o filenames\n", buffer.str());
+            CPPUNIT_ASSERT_EQUAL("COMPREPLY=('" % iniFilePath % ".ini' '" % mkvFilePath + " '\"'\"'with quote'\"'\"'.mkv' ); compopt -o filenames\n", buffer.str());
         }
 
         // sub arguments
diff --git a/tests/testutils.cpp b/tests/testutils.cpp
index 35ceb12..30e2c82 100644
--- a/tests/testutils.cpp
+++ b/tests/testutils.cpp
@@ -202,7 +202,7 @@ string TestApplication::workingCopyPath(const string &name) const
     // copy file
     try {
         origFile.open(testFilePath(name), ios_base::in | ios_base::binary);
-        string path = m_workingDir + name;
+        const string path = m_workingDir + name;
         workingCopy.open(path, ios_base::out | ios_base::binary | ios_base::trunc);
         workingCopy << origFile.rdbuf();
         return path;