diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index cf468622ea6..3a108888253 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20097,7 +20097,7 @@ namespace ts {
                     const symbol = getResolvedSymbol(<Identifier>node);
                     return symbol !== unknownSymbol ? `${flowContainer ? getNodeId(flowContainer) : "-1"}|${getTypeId(declaredType)}|${getTypeId(initialType)}|${isConstraintPosition(node) ? "@" : ""}${getSymbolId(symbol)}` : undefined;
                 case SyntaxKind.ThisKeyword:
-                    return "0";
+                    return `0|${flowContainer ? getNodeId(flowContainer) : "-1"}|${getTypeId(declaredType)}|${getTypeId(initialType)}`;
                 case SyntaxKind.NonNullExpression:
                 case SyntaxKind.ParenthesizedExpression:
                     return getFlowCacheKey((<NonNullExpression | ParenthesizedExpression>node).expression, declaredType, initialType, flowContainer);
@@ -20960,7 +20960,7 @@ namespace ts {
 
         function getFlowTypeOfReference(reference: Node, declaredType: Type, initialType = declaredType, flowContainer?: Node, couldBeUninitialized?: boolean) {
             let key: string | undefined;
-            let keySet = false;
+            let isKeySet = false;
             let flowDepth = 0;
             if (flowAnalysisDisabled) {
                 return errorType;
@@ -20983,10 +20983,10 @@ namespace ts {
             return resultType;
 
             function getOrSetCacheKey() {
-                if (keySet) {
+                if (isKeySet) {
                     return key;
                 }
-                keySet = true;
+                isKeySet = true;
                 return key = getFlowCacheKey(reference, declaredType, initialType, flowContainer);
             }
 
diff --git a/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.errors.txt b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.errors.txt
new file mode 100644
index 00000000000..85f445fdde4
--- /dev/null
+++ b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.errors.txt
@@ -0,0 +1,39 @@
+tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts(29,13): error TS2322: Type 'string | number' is not assignable to type 'number'.
+  Type 'string' is not assignable to type 'number'.
+
+
+==== tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts (1 errors) ====
+    // #31995
+    type State = {
+        type: "numberVariant";
+        data: number;
+    } | {
+        type: "stringVariant";
+        data: string;
+    };
+    
+    class SomeClass {
+        state!: State;
+        method() {
+            while (0) { }
+            this.state.data;
+            if (this.state.type === "stringVariant") {
+                const s: string = this.state.data;
+            }
+        }
+    }
+    
+    class SomeClass2 {
+        state!: State;
+        method() {
+            const c = false;
+            while (c) { }
+            if (this.state.type === "numberVariant") {
+                this.state.data;
+            }
+            let n: number = this.state?.data; // This should be an error
+                ~
+!!! error TS2322: Type 'string | number' is not assignable to type 'number'.
+!!! error TS2322:   Type 'string' is not assignable to type 'number'.
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.js b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.js
new file mode 100644
index 00000000000..68ad3c5dd7c
--- /dev/null
+++ b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.js
@@ -0,0 +1,60 @@
+//// [typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts]
+// #31995
+type State = {
+    type: "numberVariant";
+    data: number;
+} | {
+    type: "stringVariant";
+    data: string;
+};
+
+class SomeClass {
+    state!: State;
+    method() {
+        while (0) { }
+        this.state.data;
+        if (this.state.type === "stringVariant") {
+            const s: string = this.state.data;
+        }
+    }
+}
+
+class SomeClass2 {
+    state!: State;
+    method() {
+        const c = false;
+        while (c) { }
+        if (this.state.type === "numberVariant") {
+            this.state.data;
+        }
+        let n: number = this.state?.data; // This should be an error
+    }
+}
+
+//// [typeOfThisInstanceMemberNarrowedWithLoopAntecedent.js]
+var SomeClass = /** @class */ (function () {
+    function SomeClass() {
+    }
+    SomeClass.prototype.method = function () {
+        while (0) { }
+        this.state.data;
+        if (this.state.type === "stringVariant") {
+            var s = this.state.data;
+        }
+    };
+    return SomeClass;
+}());
+var SomeClass2 = /** @class */ (function () {
+    function SomeClass2() {
+    }
+    SomeClass2.prototype.method = function () {
+        var _a;
+        var c = false;
+        while (c) { }
+        if (this.state.type === "numberVariant") {
+            this.state.data;
+        }
+        var n = (_a = this.state) === null || _a === void 0 ? void 0 : _a.data; // This should be an error
+    };
+    return SomeClass2;
+}());
diff --git a/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.symbols b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.symbols
new file mode 100644
index 00000000000..c36f9a19445
--- /dev/null
+++ b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.symbols
@@ -0,0 +1,95 @@
+=== tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts ===
+// #31995
+type State = {
+>State : Symbol(State, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 0, 0))
+
+    type: "numberVariant";
+>type : Symbol(type, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 1, 14))
+
+    data: number;
+>data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26))
+
+} | {
+    type: "stringVariant";
+>type : Symbol(type, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 4, 5))
+
+    data: string;
+>data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+
+};
+
+class SomeClass {
+>SomeClass : Symbol(SomeClass, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 7, 2))
+
+    state!: State;
+>state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>State : Symbol(State, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 0, 0))
+
+    method() {
+>method : Symbol(SomeClass.method, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 10, 18))
+
+        while (0) { }
+        this.state.data;
+>this.state.data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+>this.state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>this : Symbol(SomeClass, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 7, 2))
+>state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+
+        if (this.state.type === "stringVariant") {
+>this.state.type : Symbol(type, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 1, 14), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 4, 5))
+>this.state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>this : Symbol(SomeClass, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 7, 2))
+>state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>type : Symbol(type, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 1, 14), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 4, 5))
+
+            const s: string = this.state.data;
+>s : Symbol(s, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 15, 17))
+>this.state.data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+>this.state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>this : Symbol(SomeClass, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 7, 2))
+>state : Symbol(SomeClass.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 9, 17))
+>data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+        }
+    }
+}
+
+class SomeClass2 {
+>SomeClass2 : Symbol(SomeClass2, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 18, 1))
+
+    state!: State;
+>state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>State : Symbol(State, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 0, 0))
+
+    method() {
+>method : Symbol(SomeClass2.method, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 21, 18))
+
+        const c = false;
+>c : Symbol(c, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 23, 13))
+
+        while (c) { }
+>c : Symbol(c, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 23, 13))
+
+        if (this.state.type === "numberVariant") {
+>this.state.type : Symbol(type, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 1, 14), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 4, 5))
+>this.state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>this : Symbol(SomeClass2, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 18, 1))
+>state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>type : Symbol(type, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 1, 14), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 4, 5))
+
+            this.state.data;
+>this.state.data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26))
+>this.state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>this : Symbol(SomeClass2, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 18, 1))
+>state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26))
+        }
+        let n: number = this.state?.data; // This should be an error
+>n : Symbol(n, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 28, 11))
+>this.state?.data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+>this.state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>this : Symbol(SomeClass2, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 18, 1))
+>state : Symbol(SomeClass2.state, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 20, 18))
+>data : Symbol(data, Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 2, 26), Decl(typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts, 5, 26))
+    }
+}
diff --git a/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.types b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.types
new file mode 100644
index 00000000000..7938c5ec6e1
--- /dev/null
+++ b/tests/baselines/reference/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.types
@@ -0,0 +1,100 @@
+=== tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts ===
+// #31995
+type State = {
+>State : State
+
+    type: "numberVariant";
+>type : "numberVariant"
+
+    data: number;
+>data : number
+
+} | {
+    type: "stringVariant";
+>type : "stringVariant"
+
+    data: string;
+>data : string
+
+};
+
+class SomeClass {
+>SomeClass : SomeClass
+
+    state!: State;
+>state : State
+
+    method() {
+>method : () => void
+
+        while (0) { }
+>0 : 0
+
+        this.state.data;
+>this.state.data : string | number
+>this.state : State
+>this : this
+>state : State
+>data : string | number
+
+        if (this.state.type === "stringVariant") {
+>this.state.type === "stringVariant" : boolean
+>this.state.type : "numberVariant" | "stringVariant"
+>this.state : State
+>this : this
+>state : State
+>type : "numberVariant" | "stringVariant"
+>"stringVariant" : "stringVariant"
+
+            const s: string = this.state.data;
+>s : string
+>this.state.data : string
+>this.state : { type: "stringVariant"; data: string; }
+>this : this
+>state : { type: "stringVariant"; data: string; }
+>data : string
+        }
+    }
+}
+
+class SomeClass2 {
+>SomeClass2 : SomeClass2
+
+    state!: State;
+>state : State
+
+    method() {
+>method : () => void
+
+        const c = false;
+>c : false
+>false : false
+
+        while (c) { }
+>c : false
+
+        if (this.state.type === "numberVariant") {
+>this.state.type === "numberVariant" : boolean
+>this.state.type : "numberVariant" | "stringVariant"
+>this.state : State
+>this : this
+>state : State
+>type : "numberVariant" | "stringVariant"
+>"numberVariant" : "numberVariant"
+
+            this.state.data;
+>this.state.data : number
+>this.state : { type: "numberVariant"; data: number; }
+>this : this
+>state : { type: "numberVariant"; data: number; }
+>data : number
+        }
+        let n: number = this.state?.data; // This should be an error
+>n : number
+>this.state?.data : string | number
+>this.state : State
+>this : this
+>state : State
+>data : string | number
+    }
+}
diff --git a/tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts b/tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts
new file mode 100644
index 00000000000..0270eee4fe6
--- /dev/null
+++ b/tests/cases/conformance/classes/members/instanceAndStaticMembers/typeOfThisInstanceMemberNarrowedWithLoopAntecedent.ts
@@ -0,0 +1,31 @@
+// #31995
+type State = {
+    type: "numberVariant";
+    data: number;
+} | {
+    type: "stringVariant";
+    data: string;
+};
+
+class SomeClass {
+    state!: State;
+    method() {
+        while (0) { }
+        this.state.data;
+        if (this.state.type === "stringVariant") {
+            const s: string = this.state.data;
+        }
+    }
+}
+
+class SomeClass2 {
+    state!: State;
+    method() {
+        const c = false;
+        while (c) { }
+        if (this.state.type === "numberVariant") {
+            this.state.data;
+        }
+        let n: number = this.state?.data; // This should be an error
+    }
+}
\ No newline at end of file