diff --git a/tests/mbconv/mbconvtest.cpp b/tests/mbconv/mbconvtest.cpp
index 4674a67e9a..7045b3673e 100644
--- a/tests/mbconv/mbconvtest.cpp
+++ b/tests/mbconv/mbconvtest.cpp
@@ -1247,7 +1247,7 @@ void MBConvTestCase::TestStreamDecoder(
     {
         wxChar wc = textInputStream.GetChar();
         CPPUNIT_ASSERT_EQUAL_MESSAGE(
-            std::string(wxString::Format("At position %lu", (unsigned long)i)),
+            wxString::Format("At position %lu", (unsigned long)i).ToStdString(),
             wideBuffer[i],
             wc
         );
diff --git a/tests/strings/stdstrings.cpp b/tests/strings/stdstrings.cpp
index cf80f2eb5f..1446a8c040 100644
--- a/tests/strings/stdstrings.cpp
+++ b/tests/strings/stdstrings.cpp
@@ -607,8 +607,10 @@ void StdStringTestCase::StdConversion()
 #endif
     CPPUNIT_ASSERT_EQUAL( "hello", s6 );
 
+#if wxUSE_UNSAFE_WXSTRING_CONV
     std::string s7(s4);
     CPPUNIT_ASSERT( s7 == "hello" );
+#endif
 
     wxStdWideString s8(s4);
     CPPUNIT_ASSERT( s8 == "hello" );
diff --git a/tests/strings/strings.cpp b/tests/strings/strings.cpp
index aa65f71954..3562510b51 100644
--- a/tests/strings/strings.cpp
+++ b/tests/strings/strings.cpp
@@ -1028,8 +1028,10 @@ void StringTestCase::CStrDataImplicitConversion()
     // implicit conversion of wxString is not available in STL build
 #if !wxUSE_STL
     CPPUNIT_ASSERT( CheckStrConstWChar(s, s) );
+#if wxUSE_UNSAFE_WXSTRING_CONV
     CPPUNIT_ASSERT( CheckStrConstChar(s, s) );
 #endif
+#endif
 }
 
 void StringTestCase::ExplicitConversion()
diff --git a/tests/strings/unicode.cpp b/tests/strings/unicode.cpp
index 19587dd99f..04345bf199 100644
--- a/tests/strings/unicode.cpp
+++ b/tests/strings/unicode.cpp
@@ -113,7 +113,7 @@ private:
     static std::string
     Message(size_t n, const wxString& msg)
     {
-        return std::string(wxString::Format("#%lu: %s", (unsigned long)n, msg));
+        return wxString::Format("#%lu: %s", (unsigned long)n, msg).ToStdString();
     }
 
     template <typename T>