diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index dca121f59..b0d8aebb6 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -50,7 +50,7 @@ static void valueFlowBeforeCondition(TokenList *tokenlist, ErrorLogger *errorLog
         unsigned int varid;
         MathLib::bigint num;
         const Variable *var;
-        if (tok->isComparisonOp() && tok->astOperand1() && tok->astOperand2()) {
+        if (tok->isComparisonOp() && tok->astOperand2()) {
             if (tok->astOperand1()->isName() && tok->astOperand2()->isNumber()) {
                 varid = tok->astOperand1()->varId();
                 var = tok->astOperand1()->variable();
@@ -78,8 +78,8 @@ static void valueFlowBeforeCondition(TokenList *tokenlist, ErrorLogger *errorLog
         if (varid == 0U)
             continue;
 
-        // bailout: global variables
-        if (var && var->isGlobal()) {
+        // bailout: global non-const variables
+        if (var && var->isGlobal() && !var->isConst()) {
             if (settings->debugwarnings)
                 bailout(tokenlist, errorLogger, tok, "global variable " + var->nameToken()->str());
             continue;
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 4ab1bee8e..e71842c7c 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -97,6 +97,13 @@ private:
                "}";
         ASSERT_EQUALS(true, testValueOfX(code, 2U, 0));
 
+        code = "extern const int x;\n"
+               "void f() {\n"
+               "    int a = x;\n"
+               "    if (x == 123) {}\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 123));
+
         // bailout: ?:
         bailout("void f(int x) {\n"
                 "    y = ((x<0) ? x : ((x==2)?3:4));\n"