diff --git a/src/tokenize.cpp b/src/tokenize.cpp
index d13aeb137..1a9e9fd3b 100644
--- a/src/tokenize.cpp
+++ b/src/tokenize.cpp
@@ -1420,6 +1420,7 @@ void Tokenizer::simplifyTokenList()
 
     elseif();
     simplifyIfNot();
+    simplifyNot();
     simplifyIfAssign();
 
     for (Token *tok = _tokens; tok; tok = tok->next())
@@ -2233,6 +2234,25 @@ bool Tokenizer::simplifyIfNot()
     return ret;
 }
 
+
+bool Tokenizer::simplifyNot()
+{
+    // "if (not p)" => "if (!p)"
+    bool ret = false;
+    for (Token *tok = _tokens; tok; tok = tok->next())
+    {
+        if (Token::Match(tok, "if|while ( not %var%"))
+            tok->next()->next()->str("!");
+        if (Token::Match(tok, "&& not %var%"))
+            tok->next()->str("!");
+        if (Token::Match(tok, "|| not %var%"))
+            tok->next()->str("!");
+    }
+    return ret;
+}
+
+
+
 bool Tokenizer::simplifyKnownVariables()
 {
     createLinks();
diff --git a/src/tokenize.h b/src/tokenize.h
index 583cef046..a4fac3a38 100644
--- a/src/tokenize.h
+++ b/src/tokenize.h
@@ -113,6 +113,12 @@ public:
      */
     bool simplifyIfNot();
 
+    /**
+     * simplify the "not" keyword to "!"
+     * Example: "if (not p)" => "if (!p)"
+     */
+    bool simplifyNot();
+
 protected:
 
     /** Add braces to an if-block
diff --git a/test/testsimplifytokens.cpp b/test/testsimplifytokens.cpp
index 51d1addd3..2809bfa6f 100644
--- a/test/testsimplifytokens.cpp
+++ b/test/testsimplifytokens.cpp
@@ -99,6 +99,9 @@ private:
         // "if(0==x)" => "if(!x)"
         TEST_CASE(ifnot);
         TEST_CASE(combine_wstrings);
+
+        // Simplify "not" to "!" (#345)
+        TEST_CASE(not1);
     }
 
     std::string tok(const char code[])
@@ -858,6 +861,32 @@ private:
         ASSERT_EQUALS("if ( ! ( a = b ) )", simplifyIfNot("if((a=b)==0)"));
     }
 
+
+
+    std::string simplifyNot(const char code[])
+    {
+        // tokenize..
+        Tokenizer tokenizer;
+        std::istringstream istr(code);
+        tokenizer.tokenize(istr, "test.cpp");
+
+        tokenizer.simplifyNot();
+
+        std::ostringstream ostr;
+        for (const Token *tok = tokenizer.tokens(); tok; tok = tok->next())
+            ostr << (tok->previous() ? " " : "") << tok->str();
+
+        return ostr.str();
+    }
+
+    void not1()
+    {
+        ASSERT_EQUALS("if ( ! p )", simplifyNot("if (not p)"));
+        ASSERT_EQUALS("if ( p && ! q )", simplifyNot("if (p && not q)"));
+        ASSERT_EQUALS("void foo ( not i )", simplifyNot("void foo ( not i )"));
+    }
+
+
 };
 
 REGISTER_TEST(TestSimplifyTokens)