diff --git a/cli/cmdlineparser.cpp b/cli/cmdlineparser.cpp
index c5c059e9b..0792dfde3 100644
--- a/cli/cmdlineparser.cpp
+++ b/cli/cmdlineparser.cpp
@@ -699,6 +699,8 @@ bool CmdLineParser::ParseFromArgs(int argc, const char* const argv[])
                 else if (platform == "unix64")
                     _settings->platform(Settings::Unix64);
                 else if (platform == "native")
+                    _settings->platform(Settings::Native);
+                else if (platform == "unspecified")
                     _settings->platform(Settings::Unspecified);
                 else if (!_settings->platformFile(platform)) {
                     std::string message("cppcheck: error: unrecognized platform: \"");
@@ -943,8 +945,10 @@ void CmdLineParser::PrintHelp()
               "                          * win64\n"
               "                                 64 bit Windows\n"
               "                          * native\n"
-              "                                 Unspecified platform. Type sizes of host system\n"
-              "                                 are assumed, but no further assumptions.\n"
+              "                                 Type sizes of host system are assumed, but no\n"
+              "                                 further assumptions.\n"
+              "                          * unspecified\n"
+              "                                 Unknown type sizes\n"
               "    -q, --quiet          Do not show progress reports.\n"
               "    -rp, --relative-paths\n"
               "    -rp=<paths>, --relative-paths=<paths>\n"
diff --git a/lib/platform.cpp b/lib/platform.cpp
index f0ed68a30..33422aed9 100644
--- a/lib/platform.cpp
+++ b/lib/platform.cpp
@@ -36,26 +36,7 @@ cppcheck::Platform::Platform()
 bool cppcheck::Platform::platform(cppcheck::Platform::PlatformType type)
 {
     switch (type) {
-    case Unspecified:
-        platformType = type;
-        sizeof_bool = sizeof(bool);
-        sizeof_short = sizeof(short);
-        sizeof_int = sizeof(int);
-        sizeof_long = sizeof(long);
-        sizeof_long_long = sizeof(long long);
-        sizeof_float = sizeof(float);
-        sizeof_double = sizeof(double);
-        sizeof_long_double = sizeof(long double);
-        sizeof_wchar_t = sizeof(wchar_t);
-        sizeof_size_t = sizeof(std::size_t);
-        sizeof_pointer = sizeof(void *);
-        defaultSign = '\0';
-        char_bit = 8;
-        short_bit = char_bit * sizeof_short;
-        int_bit = char_bit * sizeof_int;
-        long_bit = char_bit * sizeof_long;
-        long_long_bit = char_bit * sizeof_long_long;
-        return true;
+    case Unspecified: // unknown type sizes (sizes etc are set but are not known)
     case Native: // same as system this code was compile on
         platformType = type;
         sizeof_bool = sizeof(bool);
@@ -69,7 +50,9 @@ bool cppcheck::Platform::platform(cppcheck::Platform::PlatformType type)
         sizeof_wchar_t = sizeof(wchar_t);
         sizeof_size_t = sizeof(std::size_t);
         sizeof_pointer = sizeof(void *);
-        {
+        if (type == Unspecified) {
+            defaultSign = '\0';
+        } else {
             char x = -1;
             defaultSign = (x < 0) ? 's' : 'u';
         }
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index ab96a34b1..575ebba70 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -643,7 +643,8 @@ static Token * valueFlowSetConstantValue(const Token *tok, const Settings *setti
                        type->str() == "long" ? settings->sizeof_long : 0;
             }
             ValueFlow::Value value(size);
-            value.setKnown();
+            if (settings->platformType != cppcheck::Platform::Unspecified)
+                value.setKnown();
             setTokenValue(const_cast<Token *>(tok), value, settings);
             setTokenValue(const_cast<Token *>(tok->next()), value, settings);
         } else if (tok2->type() && tok2->type()->isEnumType()) {
@@ -659,7 +660,8 @@ static Token * valueFlowSetConstantValue(const Token *tok, const Settings *setti
                 }
             }
             ValueFlow::Value value(size);
-            value.setKnown();
+            if (settings->platformType != cppcheck::Platform::Unspecified)
+                value.setKnown();
             setTokenValue(const_cast<Token *>(tok), value, settings);
             setTokenValue(const_cast<Token *>(tok->next()), value, settings);
         } else if (Token::Match(tok, "sizeof ( %var% ) / sizeof (") && tok->next()->astParent() == tok->tokAt(4)) {
@@ -674,42 +676,51 @@ static Token * valueFlowSetConstantValue(const Token *tok, const Settings *setti
                 sz1->variable()->dimensionKnown(0) &&
                 (Token::Match(sz2, "* %varid% )", varid1) || Token::Match(sz2, "%varid% [ 0 ] )", varid1))) {
                 ValueFlow::Value value(sz1->variable()->dimension(0));
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->tokAt(4)), value, settings);
             }
         } else if (!tok2->type()) {
             const ValueType &vt = ValueType::parseDecl(tok2,settings);
             if (vt.pointer) {
                 ValueFlow::Value value(settings->sizeof_pointer);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::CHAR) {
                 ValueFlow::Value value(1);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::SHORT) {
                 ValueFlow::Value value(settings->sizeof_short);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::INT) {
                 ValueFlow::Value value(settings->sizeof_int);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::LONG) {
                 ValueFlow::Value value(settings->sizeof_long);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::LONGLONG) {
                 ValueFlow::Value value(settings->sizeof_long_long);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::FLOAT) {
                 ValueFlow::Value value(settings->sizeof_float);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             } else if (vt.type == ValueType::Type::DOUBLE) {
                 ValueFlow::Value value(settings->sizeof_double);
-                value.setKnown();
+                if (settings->platformType != cppcheck::Platform::Unspecified)
+                    value.setKnown();
                 setTokenValue(const_cast<Token *>(tok->next()), value, settings);
             }
         }