diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index a698ecff4..14b53a6b2 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -2908,7 +2908,7 @@ void CheckOther::checkMathFunctions()
         }
         // sqrt( x ): if x is negative the result is undefined
         else if (tok->varId() == 0 &&
-                 Token::Match(tok, "sqrt ( %num% )") &&
+                 Token::Match(tok, "sqrt|sqrtf|sqrtl ( %num% )") &&
                  MathLib::isNegative(tok->tokAt(2)->str()))
         {
             mathfunctionCallError(tok);
@@ -3257,6 +3257,17 @@ void CheckOther::checkDuplicateExpression()
             if (Token::Match(tok, "(|&&|%oror% %var% &&|%oror%|==|!=|<=|>=|<|>|-|%or% %var% )|&&|%oror%") &&
                 tok->strAt(1) == tok->strAt(3))
             {
+                // float == float and float != float are valid NaN checks
+                if (Token::Match(tok->tokAt(2), "==|!=") && tok->next()->varId())
+                {
+                    const Variable * var = symbolDatabase->getVariableFromVarId(tok->next()->varId());
+                    if (var && var->typeStartToken() == var->typeEndToken())
+                    {
+                        if (Token::Match(var->typeStartToken(), "float|double"))
+                            continue;
+                    }
+                }
+
                 duplicateExpressionError(tok->next(), tok->tokAt(3), tok->strAt(2));
             }
             else if (Token::Match(tok, "(|&&|%oror% %var% . %var% &&|%oror%|==|!=|<=|>=|<|>|-|%or% %var% . %var% )|&&|%oror%") &&
diff --git a/test/testother.cpp b/test/testother.cpp
index 2fd0006c1..9466e0c8e 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -115,7 +115,8 @@ private:
 
         TEST_CASE(duplicateIf);
         TEST_CASE(duplicateBranch);
-        TEST_CASE(duplicateExpression);
+        TEST_CASE(duplicateExpression1);
+        TEST_CASE(duplicateExpression2); // ticket #2730
     }
 
     void check(const char code[], const char *filename = NULL)
@@ -2502,7 +2503,7 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
-    void duplicateExpression()
+    void duplicateExpression1()
     {
         check("voif foo() {\n"
               "    if (a == a) { }\n"
@@ -2523,6 +2524,27 @@ private:
                       "[test.cpp:5] -> [test.cpp:5]: (style) Same expression on both sides of '>'.\n"
                       "[test.cpp:6] -> [test.cpp:6]: (style) Same expression on both sides of '<'.\n", errout.str());
     }
+
+    void duplicateExpression2() // ticket #2730
+    {
+        check("int main()\n"
+              "{\n"
+              "    long double ldbl;\n"
+              "    double dbl, in;\n"
+              "    float  flt;\n"
+              "    int have_nan = 0;\n"
+              "    ldbl = sqrtl(-1.0);\n"
+              "    dbl = sqrt(-1.0);\n"
+              "    flt = sqrtf(-1.0);\n"
+              "    if (ldbl != ldbl) have_nan = 1;\n"
+              "    if (!(dbl == dbl)) have_nan = 1;\n"
+              "    if (flt != flt) have_nan = 1;\n"
+              "    return have_nan;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:7]: (error) Passing value -1.0 to sqrtl() leads to undefined result\n"
+                      "[test.cpp:8]: (error) Passing value -1.0 to sqrt() leads to undefined result\n"
+                      "[test.cpp:9]: (error) Passing value -1.0 to sqrtf() leads to undefined result\n", errout.str());
+    }
 };
 
 REGISTER_TEST(TestOther)