diff --git a/lib/preprocessor.cpp b/lib/preprocessor.cpp
index 974485687..278b8196f 100644
--- a/lib/preprocessor.cpp
+++ b/lib/preprocessor.cpp
@@ -1446,7 +1446,7 @@ std::list<std::string> Preprocessor::getcfgs(const std::string &filedata, const
 }
 
 
-void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &variables, std::string &condition, bool match)
+void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &cfg, std::string &condition, bool match)
 {
     Settings settings;
     Tokenizer tokenizer(&settings, NULL);
@@ -1455,8 +1455,8 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
 
     if (Token::Match(tokenizer.tokens(), "( %var% )"))
     {
-        std::map<std::string,std::string>::const_iterator var = variables.find(tokenizer.tokens()->strAt(1));
-        if (var != variables.end())
+        std::map<std::string,std::string>::const_iterator var = cfg.find(tokenizer.tokens()->strAt(1));
+        if (var != cfg.end())
         {
             const std::string &value = (*var).second;
             condition = (value == "0") ? "0" : "1";
@@ -1468,7 +1468,7 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
 
     if (Token::Match(tokenizer.tokens(), "( ! %var% )"))
     {
-        if (variables.find(tokenizer.tokens()->strAt(2)) == variables.end())
+        if (cfg.find(tokenizer.tokens()->strAt(2)) == cfg.end())
             condition = "1";
         else if (match)
             condition = "0";
@@ -1483,7 +1483,7 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
 
         if (Token::Match(tok, "defined ( %var% )"))
         {
-            if (variables.find(tok->strAt(2)) != variables.end())
+            if (cfg.find(tok->strAt(2)) != cfg.end())
                 tok->str("1");
             else if (match)
                 tok->str("0");
@@ -1497,7 +1497,7 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
 
         if (Token::Match(tok, "defined %var%"))
         {
-            if (variables.find(tok->strAt(1)) != variables.end())
+            if (cfg.find(tok->strAt(1)) != cfg.end())
                 tok->str("1");
             else if (match)
                 tok->str("0");
@@ -1507,8 +1507,8 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
             continue;
         }
 
-        const std::map<std::string, std::string>::const_iterator it = variables.find(tok->str());
-        if (it != variables.end())
+        const std::map<std::string, std::string>::const_iterator it = cfg.find(tok->str());
+        if (it != cfg.end())
         {
             if (!it->second.empty())
             {
@@ -1563,6 +1563,17 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
         }
     }
 
+    for (Token *tok = const_cast<Token *>(tokenizer.tokens()); tok; tok = tok->next())
+    {
+        if (Token::Match(tok, "(|%oror%|&& %num% &&|%oror%|)"))
+        {
+            if (tok->next()->str() != "0")
+            {
+                tok->next()->str("1");
+            }
+        }
+    }
+
     for (Token *tok = const_cast<Token *>(tokenizer.tokens()); tok; tok = tok->next())
     {
         while (Token::Match(tok, "(|%oror% %any% %oror% 1"))
@@ -1583,8 +1594,18 @@ void Preprocessor::simplifyCondition(const std::map<std::string, std::string> &v
 
 bool Preprocessor::match_cfg_def(const std::map<std::string, std::string> &cfg, std::string def)
 {
-    //std::cout << "cfg: \"" << cfg << "\"  ";
-    //std::cout << "def: \"" << def << "\"";
+/*
+    std::cout << "cfg: \"";
+    for (std::map<std::string, std::string>::const_iterator it = cfg.begin(); it != cfg.end(); ++it)
+    {
+        std::cout << it->first;
+        if (!it->second.empty())
+            std::cout << "=" << it->second;
+        std::cout << ";";
+    }
+    std::cout << "\"  ";
+    std::cout << "def: \"" << def << "\"\n";
+*/
 
     simplifyCondition(cfg, def, true);
 
@@ -1601,7 +1622,7 @@ bool Preprocessor::match_cfg_def(const std::map<std::string, std::string> &cfg,
 }
 
 
-std::string Preprocessor::getcode(const std::string &filedata, std::string cfg, const std::string &filename, const Settings *settings, ErrorLogger *errorLogger)
+std::string Preprocessor::getcode(const std::string &filedata, const std::string &cfg, const std::string &filename, const Settings *settings, ErrorLogger *errorLogger)
 {
     // For the error report
     unsigned int lineno = 0;
diff --git a/lib/preprocessor.h b/lib/preprocessor.h
index 4f9eefd7f..d02dd5130 100644
--- a/lib/preprocessor.h
+++ b/lib/preprocessor.h
@@ -93,7 +93,7 @@ public:
     /**
      * Get preprocessed code for a given configuration
      */
-    static std::string getcode(const std::string &filedata, std::string cfg, const std::string &filename, const Settings *settings, ErrorLogger *errorLogger);
+    static std::string getcode(const std::string &filedata, const std::string &cfg, const std::string &filename, const Settings *settings, ErrorLogger *errorLogger);
 
     /**
      * simplify condition
diff --git a/test/testpreprocessor.cpp b/test/testpreprocessor.cpp
index a9e4e0f53..4e19324ef 100644
--- a/test/testpreprocessor.cpp
+++ b/test/testpreprocessor.cpp
@@ -221,6 +221,10 @@ private:
 
         // inline suppression, missingInclude
         TEST_CASE(inline_suppression_for_missing_include);
+
+        // Using -D to predefine symbols
+        TEST_CASE(predefine1);
+        TEST_CASE(predefine2);
     }
 
 
@@ -2853,6 +2857,38 @@ private:
         preprocessor.preprocess(src, processedFile, cfg, "test.c", paths);
         ASSERT_EQUALS("", errout.str());
     }
+
+    void predefine1()
+    {
+        Settings settings;
+
+        const std::string src("#ifdef X || Y\n"
+                              "Fred & Wilma\n"
+                              "#endif\n");
+
+        std::string actual = Preprocessor::getcode(src, "X=1", "test.c", &settings, this);
+
+        ASSERT_EQUALS("\nFred & Wilma\n\n", actual);
+    }
+
+    void predefine2()
+    {
+        Settings settings;
+
+        const std::string src("#ifdef X && Y\n"
+                              "Fred & Wilma\n"
+                              "#endif\n");
+        {
+            std::string actual = Preprocessor::getcode(src, "X=1", "test.c", &settings, this);
+            ASSERT_EQUALS("\n\n\n", actual);
+        }
+
+        {
+            std::string actual = Preprocessor::getcode(src, "X=1;Y=2", "test.c", &settings, this);
+            ASSERT_EQUALS("\nFred & Wilma\n\n", actual);
+        }
+    }
+
 };
 
 REGISTER_TEST(TestPreprocessor)