diff --git a/lib/checkcondition.cpp b/lib/checkcondition.cpp
index ad547cf543e..371d46059ab 100644
--- a/lib/checkcondition.cpp
+++ b/lib/checkcondition.cpp
@@ -327,8 +327,10 @@ void CheckConditionImpl::checkBadBitmaskCheck()
             const bool isTrue = (tok->astOperand1()->hasKnownIntValue() && tok->astOperand1()->getKnownIntValue() != 0) ||
                                 (tok->astOperand2()->hasKnownIntValue() && tok->astOperand2()->getKnownIntValue() != 0);
 
-            if (isBoolean && isTrue)
+            if (isBoolean && isTrue) {
                 badBitmaskCheckError(tok);
+                diag(tok);
+            }
 
             // If there are #ifdef in the expression don't warn about redundant | to avoid FP
             const auto& startStop = tok->findExpressionStartEndTokens();
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 4be7a13dbc7..e7f70d0b619 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -1089,11 +1089,30 @@ static void valueFlowImpossibleValues(TokenList& tokenList, const Settings& sett
                 setTokenValue(tok, std::move(value), settings);
             }
 
-        } else if (Token::simpleMatch(tok, "%") && tok->astOperand2() && tok->astOperand2()->hasKnownIntValue()) {
+        } else if (tok->isBinaryOp() && tok->str() == "%" && tok->astOperand2()->hasKnownIntValue()) {
             ValueFlow::Value value{tok->astOperand2()->getKnownIntValue()};
             value.bound = ValueFlow::Value::Bound::Lower;
             value.setImpossible();
             setTokenValue(tok, std::move(value), settings);
+        } else if (tok->isBinaryOp() && tok->str() == "|") {
+            bool nonNull = false;
+            for (const Token *op : {tok->astOperand1(), tok->astOperand2()}) {
+                for (const ValueFlow::Value& v : op->values()) {
+                    if (v.valueType != ValueFlow::Value::ValueType::INT)
+                        continue;
+                    if ((v.isKnown() && v.intvalue != 0) || (v.isImpossible() && v.intvalue == 0)) {
+                        nonNull = true;
+                        break;
+                    }
+                }
+                if (nonNull)
+                    break;
+            }
+            if (nonNull) {
+                ValueFlow::Value value{0};
+                value.setImpossible();
+                setTokenValue(tok, std::move(value), settings);
+            }
         } else if (Token::Match(tok, "abs|labs|llabs|fabs|fabsf|fabsl (")) {
             ValueFlow::Value value{-1};
             value.bound = ValueFlow::Value::Bound::Upper;
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index abef2d95614..1694c608a73 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -5011,6 +5011,20 @@ class TestCondition : public TestFixture {
                       "[test.cpp:9:9]: (style) Condition '0b101010' is always true [knownConditionTrueFalse]\n"
                       "[test.cpp:10:9]: (style) Condition '!42' is always false [knownConditionTrueFalse]\n",
                       errout_str());
+
+        check("void f(int i) {\n" // #15144
+              "    int c = i | 1;\n"
+              "    if (c) {}\n"
+              "}\n"
+              "void g(int i, int m) {\n"
+              "    if (m == 0)\n"
+              "        return;\n"
+              "    int c = i | m;\n"
+              "    if (c) {}\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3:9]: (style) Condition 'c' is always true [knownConditionTrueFalse]\n"
+                      "[test.cpp:9:9]: (style) Condition 'c' is always true [knownConditionTrueFalse]\n",
+                      errout_str());
     }
 
     void alwaysTrueSymbolic()
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 3609bf2aee2..66c2f5b61c5 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -57,6 +57,7 @@ class TestValueFlow : public TestFixture {
         TEST_CASE(valueFlowMove);
 
         TEST_CASE(valueFlowBitAnd);
+        TEST_CASE(valueFlowBitOr);
         TEST_CASE(valueFlowRightShift);
 
         TEST_CASE(valueFlowCalculations);
@@ -4332,6 +4333,13 @@ class TestValueFlow : public TestFixture {
                "}\n";
         auto values = tokenValues(code, "s :", ValueFlow::Value::ValueType::FLOAT);
         ASSERT_EQUALS(0, values.size());
+
+        code = "bool f(unsigned a, unsigned b) {\n"
+               "    unsigned m = a < b ? a : b;\n"
+               "    bool x = (m > a);\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfX(code, 4U, 0));
     }
 
     void valueFlowForwardLambda() {
@@ -4423,6 +4431,16 @@ class TestValueFlow : public TestFixture {
         ASSERT_EQUALS(false, testValueOfX(code,3U,16));
     }
 
+    void valueFlowBitOr() {
+        const char *code;
+
+        code = "int f(int a) {\n"
+               "  int x = a | 0x80;\n"
+               "  return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, 0));
+    }
+
     void valueFlowForwardInconclusiveImpossible() {
         const char *code;