diff --git a/lib/cppcheck.cpp b/lib/cppcheck.cpp
index 17053c0c6..b15a21d15 100644
--- a/lib/cppcheck.cpp
+++ b/lib/cppcheck.cpp
@@ -247,10 +247,10 @@ unsigned int CppCheck::check(const std::string &path)
         const std::string clang = Path::isCPP(path) ? "clang++" : "clang";
 
         /* Experimental: import clang ast dump */
-        std::ofstream fout("temp.c");
+        std::ofstream fout("__temp__.c");
         fout << "int x;\n";
         fout.close();
-        const std::string cmd1 = clang + " -v -fsyntax-only temp.c 2>&1";
+        const std::string cmd1 = clang + " -v -fsyntax-only __temp__.c 2>&1";
         const std::pair<bool, std::string> res1 = executeCommand(cmd1);
         if (!res1.first) {
             std::cerr << "Failed to execute '" + cmd1 + "'" << std::endl;
@@ -287,7 +287,7 @@ unsigned int CppCheck::check(const std::string &path)
         Tokenizer tokenizer(&mSettings, this);
         tokenizer.list.appendFileIfNew(path);
         clangimport::parseClangAstDump(&tokenizer, ast);
-        //ValueFlow::setValues(&tokenizer.list, const_cast<SymbolDatabase *>(tokenizer.getSymbolDatabase()), this, &mSettings);
+        ValueFlow::setValues(&tokenizer.list, const_cast<SymbolDatabase *>(tokenizer.getSymbolDatabase()), this, &mSettings);
         if (mSettings.debugnormal)
             tokenizer.printDebugOutput(1);
 
diff --git a/lib/programmemory.cpp b/lib/programmemory.cpp
index a1d43d0d6..a248c8a1f 100644
--- a/lib/programmemory.cpp
+++ b/lib/programmemory.cpp
@@ -339,7 +339,7 @@ void execute(const Token *expr,
                 if (intValue == 0 &&
                     expr->str() == "--" &&
                     expr->astOperand1()->variable() &&
-                    expr->astOperand1()->variable()->typeStartToken()->isUnsigned())
+                    expr->astOperand1()->variable()->isUnsigned())
                     *error = true; // overflow
                 *result = intValue + (expr->str() == "++" ? 1 : -1);
                 programMemory->setIntValue(expr->astOperand1()->varId(), *result);
diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 9690cb3b3..d83497ed1 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -1766,6 +1766,11 @@ bool Variable::isPointerArray() const
     return isArray() && nameToken() && nameToken()->previous() && (nameToken()->previous()->str() == "*");
 }
 
+bool Variable::isUnsigned() const
+{
+    return mValueType ? (mValueType->sign == ValueType::Sign::UNSIGNED) : mTypeStartToken->isUnsigned();
+}
+
 const Token * Variable::declEndToken() const
 {
     Token const * declEnd = typeStartToken();
diff --git a/lib/symboldatabase.h b/lib/symboldatabase.h
index 189b3fa4a..dbc39eb55 100644
--- a/lib/symboldatabase.h
+++ b/lib/symboldatabase.h
@@ -480,6 +480,12 @@ public:
         return getFlag(fIsRValueRef);
     }
 
+    /**
+     * Is variable unsigned.
+     * @return true only if variable _is_ unsigned. if the sign is unknown, false is returned.
+     */
+    bool isUnsigned() const;
+
     /**
      * Does variable have a default value.
      * @return true if has a default falue, false if not
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 0ab3069e9..24e825712 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -2003,7 +2003,7 @@ static void valueFlowBeforeCondition(TokenList *tokenlist, SymbolDatabase *symbo
             val.varId = varid;
             ValueFlow::Value val2;
             if (num==1U && Token::Match(tok,"<=|>=")) {
-                if (var->typeStartToken()->isUnsigned()) {
+                if (var->isUnsigned()) {
                     val2 = ValueFlow::Value(tok,0);
                     val2.varId = varid;
                 }