diff --git a/lib/programmemory.h b/lib/programmemory.h
index bb68a9404d4..95effc70874 100644
--- a/lib/programmemory.h
+++ b/lib/programmemory.h
@@ -102,7 +102,7 @@ struct ExprIdToken {
 };
 
 struct CPPCHECKLIB ProgramMemory {
-    using Map = std::unordered_map<ExprIdToken, ValueFlow::Value, ExprIdToken::Hash>;
+    using Map = std::map<ExprIdToken, ValueFlow::Value>;
 
     ProgramMemory() : mValues(new Map()) {}
 
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index fae9c8fce13..f0764dd2bd6 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -5174,6 +5174,15 @@ class TestCondition : public TestFixture {
         TODO_ASSERT_EQUALS("",
                            "[test.cpp:11:14]: (style) Condition 'p->i==o' is always true [knownConditionTrueFalse]\n",
                            errout_str());
+
+        check("void f(int x) {\n" // #12320
+              "    int a = 0, b = 0, c = 0;\n"
+              "    a = x;\n"
+              "    if (a) b = x;\n"
+              "    if (b) c = x;\n"
+              "    if (c) {}\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void alwaysTrueInfer() {