diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index bf4c3487d..703679231 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -440,7 +440,11 @@ static void setTokenValue(Token* tok, const ValueFlow::Value &value, const Setti
         // .empty, .size, +"abc", +'a'
         if (Token::Match(parent, "+|==|!=") && parent->astOperand1() && parent->astOperand2()) {
             for (const ValueFlow::Value &value1 : parent->astOperand1()->values()) {
+                if (value1.isImpossible())
+                    continue;
                 for (const ValueFlow::Value &value2 : parent->astOperand2()->values()) {
+                    if (value2.isImpossible())
+                        continue;
                     if (value1.path != value2.path)
                         continue;
                     ValueFlow::Value result;
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 8cd4cfd6f..e0fd9bd4c 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -5026,6 +5026,17 @@ private:
                "}\n";
         ASSERT_EQUALS(true, testValueOfXKnown(code, 4U, 0));
 
+        code = "bool f(std::string s) {\n"
+               "    if (!s.empty()) {\n"
+               "        bool x = s == \"0\";\n"
+               "        return x;\n"
+               "    }\n"
+               "    return false;\n"
+               "}\n";
+        ASSERT_EQUALS(false, testValueOfXKnown(code, 4U, 0));
+        ASSERT_EQUALS(false, testValueOfXKnown(code, 4U, 1));
+        ASSERT_EQUALS(false, testValueOfXImpossible(code, 4U, 0));
+
         code = "std::vector<int> g();\n"
                "int f(bool b) {\n"
                "    std::set<int> a;\n"