diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index ab02389b6..33bcd3de6 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -148,8 +148,8 @@ static bool isOppositeCond(const Token * const cond1, const Token * const cond2,
     if (isSameExpression(cond1->astOperand1(), cond2->astOperand1(), constFunctions) &&
         isSameExpression(cond1->astOperand2(), cond2->astOperand2(), constFunctions)) {
         comp2 = cond2->str();
-    } else if (isSameExpression(cond1->astOperand1(), cond2->astOperand1(), constFunctions) &&
-               isSameExpression(cond1->astOperand2(), cond2->astOperand2(), constFunctions)) {
+    } else if (isSameExpression(cond1->astOperand1(), cond2->astOperand2(), constFunctions) &&
+               isSameExpression(cond1->astOperand2(), cond2->astOperand1(), constFunctions)) {
         comp2 = cond2->str();
         if (comp2[0] == '>')
             comp2[0] = '<';
@@ -3342,7 +3342,8 @@ void CheckOther::oppositeInnerCondition()
             }
             if (Token::Match(tok,"%type% (") && nonlocal) // function call -> bailout if there are nonlocal variables
                 break;
-            else if (tok->varId() && vars.find(tok->varId()) != vars.end()) {
+            else if ((tok->varId() && vars.find(tok->varId()) != vars.end()) ||
+                     (!tok->varId() && nonlocal)) {
                 if (Token::Match(tok, "%var% ++|--|="))
                     break;
                 if (Token::Match(tok->previous(), "++|--|& %var%"))
diff --git a/test/testother.cpp b/test/testother.cpp
index a5ca3d8be..398571629 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -302,6 +302,13 @@ private:
               "}");
         ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (warning) Opposite conditions in nested 'if' blocks lead to a dead code block.\n", errout.str());
 
+        check("void foo(int a, int b) {\n"
+              "    if(a==b)\n"
+              "        if(b!=a)\n"
+              "            cout << a;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (warning) Opposite conditions in nested 'if' blocks lead to a dead code block.\n", errout.str());
+
         check("void foo(int a) {\n"
               "    if(a >= 50) {\n"
               "        if(a < 50)\n"
@@ -402,6 +409,14 @@ private:
               "}");
         ASSERT_EQUALS("", errout.str());
 
+        // #5750 - another fp when undeclared variable is used
+        check("void f() {\n"
+              "   if (r < w){\n"
+              "       r += 3;\n"
+              "       if (r > w) {}\n"
+              "    }\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void emptyBrackets() {