diff --git a/lib/checkio.cpp b/lib/checkio.cpp
index 111a22383..81e6b41d6 100644
--- a/lib/checkio.cpp
+++ b/lib/checkio.cpp
@@ -407,6 +407,7 @@ void CheckIO::checkWrongPrintfScanfArguments()
 {
     const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
     bool warning = _settings->isEnabled("warning");
+    bool windows = _settings->isWindowsPlatform();
 
     std::size_t functions = symbolDatabase->functionScopes.size();
     for (std::size_t j = 0; j < functions; ++j) {
@@ -437,7 +438,11 @@ void CheckIO::checkWrongPrintfScanfArguments()
 
             if (!formatString.empty()) {
                 /* formatstring found in library */
-            } else if (Token::Match(tok, "printf|scanf|wprintf|wscanf ( %str%")) {
+            } else if (Token::Match(tok, "printf|scanf|wprintf|wscanf ( %str%") ||
+                       (windows && (Token::Match(tok, "Format|AppendFormat ( %str%") &&
+                                    Token::Match(tok->tokAt(-2), "%var% .") && tok->tokAt(-2)->variable() &&
+                                    tok->tokAt(-2)->variable()->typeStartToken()->str() == "CString"))) {
+
                 formatString = tok->strAt(2);
                 if (tok->strAt(3) == ",") {
                     argListTok = tok->tokAt(4);
diff --git a/lib/settings.h b/lib/settings.h
index b6a7efc2b..23d02651e 100644
--- a/lib/settings.h
+++ b/lib/settings.h
@@ -240,6 +240,16 @@ public:
 
     /** set the platform type for user specified platforms */
     bool platformFile(const std::string &filename);
+
+    /**
+     * @brief Returns true if platform type is Windows
+     * @return true if Windows platform type.
+     */
+    bool isWindowsPlatform() const {
+        return platformType == Win32A ||
+               platformType == Win32W ||
+               platformType == Win64;
+    }
 };
 
 /// @}
diff --git a/test/testio.cpp b/test/testio.cpp
index 1a880ae1c..6eb5091c0 100644
--- a/test/testio.cpp
+++ b/test/testio.cpp
@@ -49,6 +49,7 @@ private:
         TEST_CASE(testPosixPrintfScanfParameterPosition);  // #4900
 
         TEST_CASE(testMicrosoftPrintfArgument); // ticket #4902
+        TEST_CASE(testMicrosoftCStringFormatArguments); // ticket #4920
 
         TEST_CASE(testlibrarycfg); // library configuration
     }
@@ -2132,6 +2133,33 @@ private:
                       "[test.cpp:17]: (warning) 'I64' in format string (no. 1) is a length modifier and cannot be used without a conversion specifier.\n", errout.str());
     }
 
+    void testMicrosoftCStringFormatArguments() { // ticket #4920
+        check("void foo() {\n"
+              "    unsigned __int32 u32;\n"
+              "    String string;\n"
+              "    string.Format(\"%I32d\", u32);\n"
+              "    string.AppendFormat(\"%I32d\", u32);\n"
+              "}", false, false, Settings::Win32A);
+        ASSERT_EQUALS("", errout.str());
+
+        check("void foo() {\n"
+              "    unsigned __int32 u32;\n"
+              "    CString string;\n"
+              "    string.Format(\"%I32d\", u32);\n"
+              "    string.AppendFormat(\"%I32d\", u32);\n"
+              "}", false, false, Settings::Unix32);
+        ASSERT_EQUALS("", errout.str());
+
+        check("void foo() {\n"
+              "    unsigned __int32 u32;\n"
+              "    CString string;\n"
+              "    string.Format(\"%I32d\", u32);\n"
+              "    string.AppendFormat(\"%I32d\", u32);\n"
+              "}", false, false, Settings::Win32A);
+        ASSERT_EQUALS("[test.cpp:4]: (warning) %I32d in format string (no. 1) requires a signed integer but the argument type is 'unsigned __int32 {aka unsigned int}'.\n"
+                      "[test.cpp:5]: (warning) %I32d in format string (no. 1) requires a signed integer but the argument type is 'unsigned __int32 {aka unsigned int}'.\n", errout.str());
+    }
+
     void testlibrarycfg() {
         const char code[] = "void f() {\n"
                             "    format(\"%s\");\n"