diff --git a/src/libs/cplusplus/pp-engine.cpp b/src/libs/cplusplus/pp-engine.cpp
index fa96c54176d8279c489d2694adeadac87f1a51b5..93a6e451b4d3950da28abed2b1bfa38b991be577 100644
--- a/src/libs/cplusplus/pp-engine.cpp
+++ b/src/libs/cplusplus/pp-engine.cpp
@@ -2129,7 +2129,7 @@ void Preprocessor::maybeStartOutputLine()
     // If previous line ends with \ (possibly followed by whitespace), add another \n
     const char *start = buffer.constData();
     const char *ch = start + buffer.length() - 2;
-    while (ch > start && (*ch != '\n') && std::isspace(*ch))
+    while (ch > start && (*ch != '\n') && pp_isspace(*ch))
         --ch;
     if (*ch == '\\')
         buffer.append('\n');
diff --git a/tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp b/tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp
index 376716a9e788eee355f883b274290e099313b137..47eb297ded260cc351db714eed04de1dfe9fd8c9 100644
--- a/tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp
+++ b/tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp
@@ -409,6 +409,7 @@ private slots:
     void undef();
     void concat();
     void excessive_nesting();
+    void multi_byte_code_point_in_expansion();
 };
 
 // Remove all #... lines, and 'simplify' string, to allow easily comparing the result
@@ -2064,6 +2065,26 @@ void tst_Preprocessor::excessive_nesting()
     QCOMPARE(prep, output);
 }
 
+void tst_Preprocessor::multi_byte_code_point_in_expansion()
+{
+    Environment env;
+    Preprocessor preprocess(0, &env);
+    const QByteArray input =
+        "#define FOO(x) x\n"
+        "FOO(arg" UC_U00FC "\n)\n";
+
+    const QByteArray actual = preprocess.run(QLatin1String("<stdin>"), input);
+
+    const QByteArray expected =
+        "# 1 \"<stdin>\"\n"
+        "\n"
+        "# expansion begin 17,3 2:4\n"
+        "arg" UC_U00FC "\n"
+        "# expansion end\n"
+        "# 4 \"<stdin>\"\n";
+    QCOMPARE(actual, expected);
+}
+
 void tst_Preprocessor::compare_input_output(bool keepComments)
 {
     QFETCH(QByteArray, input);