diff --git a/lib/programmemory.cpp b/lib/programmemory.cpp
index 3a140424fd9..cbe4d34c535 100644
--- a/lib/programmemory.cpp
+++ b/lib/programmemory.cpp
@@ -1341,6 +1341,8 @@ namespace {
 
             for (const auto& p : *pm) {
                 const Token* tok = p.first.tok;
+                if (!tok)
+                    continue;
                 const ValueFlow::Value& value = p.second;
 
                 if (tok->str() == expr->str() && !astHasExpr(tok, expr->exprId())) {
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 315cc73c3d0..df9f50dcdbe 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -7275,6 +7275,17 @@ class TestValueFlow : public TestFixture {
                "    if (a && b) {}\n"
                "}\n";
         valueOfTok(code, "a");
+
+        code = "void g(const char* fmt, ...);\n" // #12255
+               "void f(const char* fmt, const char* msg) {\n"
+               "    const char* p = msg;\n"
+               "    g(\"%s\", msg);\n"
+               "}\n"
+               "void g(const char* fmt, ...) {\n"
+               "    const char* q = fmt;\n"
+               "    if (*q > 0 && *q < 100) {}\n"
+               "}\n";
+        valueOfTok(code, "&&");
     }
 
     void valueFlowHang() {