diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 2516b1cd1..a2958a0fb 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -4482,7 +4482,10 @@ bool Tokenizer::simplifyKnownVariables()
                         break;
 
                     // Using the variable in condition..
-                    if (Token::Match(tok3, "(|!|==|!=|<|<=|>|>= %varid% )|==|!=|<|<=|>|>=", varid))
+                    if (Token::Match(tok3->previous(), "if ( %varid% ==|!=|<|<=|>|>=|)", varid) ||
+                        Token::Match(tok3, "( %varid% ==|!=|<|<=|>|>=", varid) ||
+                        Token::Match(tok3, "!|==|!=|<|<=|>|>= %varid% ==|!=|<|<=|>|>=|)", varid) ||
+                        Token::Match(tok3->previous(), "strlen|free ( %varid% )", varid))
                     {
                         tok3 = tok3->next();
                         tok3->str(value);
diff --git a/test/testsimplifytokens.cpp b/test/testsimplifytokens.cpp
index 048a758df..6cc5ef551 100644
--- a/test/testsimplifytokens.cpp
+++ b/test/testsimplifytokens.cpp
@@ -3268,14 +3268,14 @@ private:
                                 "{\n"
                                 "    char buf[100];\n"
                                 "    char *p = buf;\n"
-                                "    x(p);\n"
+                                "    free(p);\n"
                                 "}\n";
 
             const char expected[] = "void f ( ) "
                                     "{ "
                                     "char buf [ 100 ] ; "
                                     "; ; "
-                                    "x ( buf ) ; "
+                                    "free ( buf ) ; "
                                     "}";
 
             ASSERT_EQUALS(expected, tok(code));
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index 3ac625337..2866bdaa9 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -786,8 +786,9 @@ private:
                             "    if ( g(a));\n"
                             "}\n";
 
+        // TODO: if a is passed by value is is ok to simplify..
         ASSERT_EQUALS(
-            "void f ( ) { int a ; a = 4 ; if ( g ( 4 ) ) { ; } }",
+            "void f ( ) { int a ; a = 4 ; if ( g ( a ) ) { ; } }",
             simplifyKnownVariables(code));
     }
 
@@ -911,11 +912,11 @@ private:
                                 "  {\n"
                                 "  }\n"
                                 "\n"
-                                "  a(b);\n"
+                                "  return b;\n"
                                 "}\n";
 
             ASSERT_EQUALS(
-                "void f ( ) { int b ; b = 0 ; b = 1 ; for ( int i = 0 ; i < 10 ; i ++ ) { } a ( 1 ) ; }",
+                "void f ( ) { int b ; b = 0 ; b = 1 ; for ( int i = 0 ; i < 10 ; i ++ ) { } return 1 ; }",
                 simplifyKnownVariables(code));
         }
     }