diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index da40345db..4ec4a651f 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -1146,13 +1146,16 @@ static bool valueFlowForward(Token * const               startToken,
                 }
             }
 
+            const Token * const condTok = tok2->next()->astOperand2();
+            const bool condAlwaysTrue = (condTok && condTok->values.size() == 1U && condTok->values.front().isKnown() && condTok->values.front().intvalue != 0);
+
             // Should scope be skipped because variable value is checked?
             std::list<ValueFlow::Value> truevalues;
             for (std::list<ValueFlow::Value>::const_iterator it = values.begin(); it != values.end(); ++it) {
-                if (!conditionIsFalse(tok2->next()->astOperand2(), getProgramMemory(tok2, varid, *it)))
+                if (condAlwaysTrue || !conditionIsFalse(condTok, getProgramMemory(tok2, varid, *it)))
                     truevalues.push_back(*it);
             }
-            if (truevalues.size() != values.size()) {
+            if (truevalues.size() != values.size() || condAlwaysTrue) {
                 // '{'
                 Token * const startToken1 = tok2->linkAt(1)->next();
 
@@ -1171,6 +1174,10 @@ static bool valueFlowForward(Token * const               startToken,
 
                 // goto '}'
                 tok2 = startToken1->link();
+
+                if (condAlwaysTrue && isReturn(tok2))
+                    return false;
+
                 continue;
             }
 
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 86e2d8061..03c0779e0 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -829,11 +829,18 @@ private:
 
         code = "void f() {\n"
                "  X *x = getx();\n"
-               "  if(false) { x = 0; }\n"
+               "  if(0) { x = 0; }\n"
                "  else { x->y = 1; }\n"
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 4U, 0));
 
+        code = "void f() {\n" // #6239
+               "  int x = 4;\n"
+               "  if(1) { x = 0; }\n"
+               "  a = x;\n"
+               "}";
+        ASSERT_EQUALS(false, testValueOfX(code, 4U, 4));
+
         code = "void f() {\n"
                "    int x = 32;\n"
                "    if (x>=32) return;\n"