diff --git a/lib/checkstring.cpp b/lib/checkstring.cpp
index 690356535..c9dd8760b 100644
--- a/lib/checkstring.cpp
+++ b/lib/checkstring.cpp
@@ -40,18 +40,18 @@ void CheckString::checkAlwaysTrueOrFalseStringCompare()
 
     for (const Token* tok = _tokenizer->tokens(); tok; tok = tok->next()) {
         if (Token::Match(tok, "memcmp|strncmp|strcmp|stricmp|strverscmp|bcmp|strcmpi|strcasecmp|strncasecmp|strncasecmp_l|strcasecmp_l|wcsncasecmp|wcscasecmp|wmemcmp|wcscmp|wcscasecmp_l|wcsncasecmp_l|wcsncmp|_mbscmp|_memicmp|_memicmp_l|_stricmp|_wcsicmp|_mbsicmp|_stricmp_l|_wcsicmp_l|_mbsicmp_l (")) {
-            if (Token::Match(tok->tokAt(2), "%str% , %str%")) {
+            if (Token::Match(tok->tokAt(2), "%str% , %str% ,|)")) {
                 const std::string &str1 = tok->strAt(2);
                 const std::string &str2 = tok->strAt(4);
                 alwaysTrueFalseStringCompareError(tok, str1, str2);
                 tok = tok->tokAt(5);
-            } else if (Token::Match(tok->tokAt(2), "%var% , %var%")) {
+            } else if (Token::Match(tok->tokAt(2), "%var% , %var% ,|)")) {
                 const std::string &str1 = tok->strAt(2);
                 const std::string &str2 = tok->strAt(4);
                 if (str1 == str2)
                     alwaysTrueStringVariableCompareError(tok, str1, str2);
                 tok = tok->tokAt(5);
-            } else if (Token::Match(tok->tokAt(2), "%var% . c_str ( ) , %var% . c_str ( )")) {
+            } else if (Token::Match(tok->tokAt(2), "%var% . c_str ( ) , %var% . c_str ( ) ,|)")) {
                 const std::string &str1 = tok->strAt(2);
                 const std::string &str2 = tok->strAt(8);
                 if (str1 == str2)
diff --git a/test/teststring.cpp b/test/teststring.cpp
index b7f3db7bf..8c044866f 100644
--- a/test/teststring.cpp
+++ b/test/teststring.cpp
@@ -125,6 +125,27 @@ private:
                       "[test.cpp:12]: (warning) Unnecessary comparison of static strings.\n"
                       "[test.cpp:13]: (warning) Unnecessary comparison of static strings.\n", errout.str());
 
+        // avoid false positives when the address is modified #6415
+        check("void f(void *p, int offset)  {\n"
+              "     if (!memcmp(p, p+offset, 42)){}\n"
+              "     if (!memcmp(p+offset, p, 42)){}\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        // avoid false positives when the address is modified #6415
+        check("void f(char *c, int offset)  {\n"
+              "     if (!memcmp(c, c + offset, 42)){}\n"
+              "     if (!memcmp(c+ offset, c , 42)){}\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        // avoid false positives when the address is modified #6415
+        check("void f(std::string s, int offset)  {\n"
+              "     if (!memcmp(s.c_str(), s.c_str() + offset, 42)){}\n"
+              "     if (!memcmp(s.c_str() + offset, s.c_str(), 42)){}\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
         check_preprocess_suppress(
             "#define MACRO \"00FF00\"\n"
             "int main()\n"