diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 1ce1b7bfec6e8..292bfe51340db 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -1181,7 +1181,6 @@ namespace ts {
                 }
                 const preCaseLabel = createBranchLabel();
                 addAntecedent(preCaseLabel, createFlowSwitchClause(preSwitchCaseFlow!, node.parent, clauseStart, i + 1));
-                addAntecedent(preCaseLabel, createFlowSwitchClause(preSwitchCaseFlow!, node.parent, clauseStart, i + 1));
                 addAntecedent(preCaseLabel, fallthroughFlow);
                 currentFlow = finishFlowLabel(preCaseLabel);
                 const clause = clauses[i];
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 852bf39c16d77..c37066858a05d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -14972,9 +14972,12 @@ namespace ts {
             }
 
             function getTypeAtSwitchClause(flow: FlowSwitchClause): FlowType {
+                const expr = flow.switchStatement.expression;
+                if (containsMatchingReferenceDiscriminant(reference, expr)) {
+                    return declaredType;
+                }
                 const flowType = getTypeAtFlowNode(flow.antecedent);
                 let type = getTypeFromFlowType(flowType);
-                const expr = flow.switchStatement.expression;
                 if (isMatchingReference(reference, expr)) {
                     type = narrowTypeBySwitchOnDiscriminant(type, flow.switchStatement, flow.clauseStart, flow.clauseEnd);
                 }
diff --git a/tests/baselines/reference/discriminantPropertyCheck.errors.txt b/tests/baselines/reference/discriminantPropertyCheck.errors.txt
index 33bdb6ea731ac..a57e17ed81ead 100644
--- a/tests/baselines/reference/discriminantPropertyCheck.errors.txt
+++ b/tests/baselines/reference/discriminantPropertyCheck.errors.txt
@@ -73,4 +73,37 @@ tests/cases/compiler/discriminantPropertyCheck.ts(65,9): error TS2532: Object is
             ~~~~~
 !!! error TS2532: Object is possibly 'undefined'.
         }
-    }
\ No newline at end of file
+    }
+    
+    // Repro from #27493
+    
+    enum Types { Str = 1, Num = 2 }
+    
+    type Instance = StrType | NumType;
+    
+    interface StrType {
+        type: Types.Str;
+        value: string;
+        length: number;
+    }
+    
+    interface NumType {
+        type: Types.Num;
+        value: number;
+    }
+    
+    function func2(inst: Instance) {
+        while (true) {
+            switch (inst.type) {
+                case Types.Str: {
+                    inst.value.length;
+                    break;
+                }
+                case Types.Num: {
+                    inst.value.toExponential;
+                    break;
+                }
+            }
+        }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/discriminantPropertyCheck.js b/tests/baselines/reference/discriminantPropertyCheck.js
index b946fe520494d..e58f28dc5a1c9 100644
--- a/tests/baselines/reference/discriminantPropertyCheck.js
+++ b/tests/baselines/reference/discriminantPropertyCheck.js
@@ -65,7 +65,40 @@ function foo6(x: Item) {
     if (x.foo !== undefined && x.qux) {
         x.foo.length;  // Error, intervening discriminant guard
     }
-}
+}
+
+// Repro from #27493
+
+enum Types { Str = 1, Num = 2 }
+
+type Instance = StrType | NumType;
+
+interface StrType {
+    type: Types.Str;
+    value: string;
+    length: number;
+}
+
+interface NumType {
+    type: Types.Num;
+    value: number;
+}
+
+function func2(inst: Instance) {
+    while (true) {
+        switch (inst.type) {
+            case Types.Str: {
+                inst.value.length;
+                break;
+            }
+            case Types.Num: {
+                inst.value.toExponential;
+                break;
+            }
+        }
+    }
+}
+
 
 //// [discriminantPropertyCheck.js]
 function goo1(x) {
@@ -108,3 +141,23 @@ function foo6(x) {
         x.foo.length; // Error, intervening discriminant guard
     }
 }
+// Repro from #27493
+var Types;
+(function (Types) {
+    Types[Types["Str"] = 1] = "Str";
+    Types[Types["Num"] = 2] = "Num";
+})(Types || (Types = {}));
+function func2(inst) {
+    while (true) {
+        switch (inst.type) {
+            case Types.Str: {
+                inst.value.length;
+                break;
+            }
+            case Types.Num: {
+                inst.value.toExponential;
+                break;
+            }
+        }
+    }
+}
diff --git a/tests/baselines/reference/discriminantPropertyCheck.symbols b/tests/baselines/reference/discriminantPropertyCheck.symbols
index 66ef653ac0d91..564cc55e3d362 100644
--- a/tests/baselines/reference/discriminantPropertyCheck.symbols
+++ b/tests/baselines/reference/discriminantPropertyCheck.symbols
@@ -228,3 +228,86 @@ function foo6(x: Item) {
 >length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
     }
 }
+
+// Repro from #27493
+
+enum Types { Str = 1, Num = 2 }
+>Types : Symbol(Types, Decl(discriminantPropertyCheck.ts, 66, 1))
+>Str : Symbol(Types.Str, Decl(discriminantPropertyCheck.ts, 70, 12))
+>Num : Symbol(Types.Num, Decl(discriminantPropertyCheck.ts, 70, 21))
+
+type Instance = StrType | NumType;
+>Instance : Symbol(Instance, Decl(discriminantPropertyCheck.ts, 70, 31))
+>StrType : Symbol(StrType, Decl(discriminantPropertyCheck.ts, 72, 34))
+>NumType : Symbol(NumType, Decl(discriminantPropertyCheck.ts, 78, 1))
+
+interface StrType {
+>StrType : Symbol(StrType, Decl(discriminantPropertyCheck.ts, 72, 34))
+
+    type: Types.Str;
+>type : Symbol(StrType.type, Decl(discriminantPropertyCheck.ts, 74, 19))
+>Types : Symbol(Types, Decl(discriminantPropertyCheck.ts, 66, 1))
+>Str : Symbol(Types.Str, Decl(discriminantPropertyCheck.ts, 70, 12))
+
+    value: string;
+>value : Symbol(StrType.value, Decl(discriminantPropertyCheck.ts, 75, 20))
+
+    length: number;
+>length : Symbol(StrType.length, Decl(discriminantPropertyCheck.ts, 76, 18))
+}
+
+interface NumType {
+>NumType : Symbol(NumType, Decl(discriminantPropertyCheck.ts, 78, 1))
+
+    type: Types.Num;
+>type : Symbol(NumType.type, Decl(discriminantPropertyCheck.ts, 80, 19))
+>Types : Symbol(Types, Decl(discriminantPropertyCheck.ts, 66, 1))
+>Num : Symbol(Types.Num, Decl(discriminantPropertyCheck.ts, 70, 21))
+
+    value: number;
+>value : Symbol(NumType.value, Decl(discriminantPropertyCheck.ts, 81, 20))
+}
+
+function func2(inst: Instance) {
+>func2 : Symbol(func2, Decl(discriminantPropertyCheck.ts, 83, 1))
+>inst : Symbol(inst, Decl(discriminantPropertyCheck.ts, 85, 15))
+>Instance : Symbol(Instance, Decl(discriminantPropertyCheck.ts, 70, 31))
+
+    while (true) {
+        switch (inst.type) {
+>inst.type : Symbol(type, Decl(discriminantPropertyCheck.ts, 74, 19), Decl(discriminantPropertyCheck.ts, 80, 19))
+>inst : Symbol(inst, Decl(discriminantPropertyCheck.ts, 85, 15))
+>type : Symbol(type, Decl(discriminantPropertyCheck.ts, 74, 19), Decl(discriminantPropertyCheck.ts, 80, 19))
+
+            case Types.Str: {
+>Types.Str : Symbol(Types.Str, Decl(discriminantPropertyCheck.ts, 70, 12))
+>Types : Symbol(Types, Decl(discriminantPropertyCheck.ts, 66, 1))
+>Str : Symbol(Types.Str, Decl(discriminantPropertyCheck.ts, 70, 12))
+
+                inst.value.length;
+>inst.value.length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
+>inst.value : Symbol(StrType.value, Decl(discriminantPropertyCheck.ts, 75, 20))
+>inst : Symbol(inst, Decl(discriminantPropertyCheck.ts, 85, 15))
+>value : Symbol(StrType.value, Decl(discriminantPropertyCheck.ts, 75, 20))
+>length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
+
+                break;
+            }
+            case Types.Num: {
+>Types.Num : Symbol(Types.Num, Decl(discriminantPropertyCheck.ts, 70, 21))
+>Types : Symbol(Types, Decl(discriminantPropertyCheck.ts, 66, 1))
+>Num : Symbol(Types.Num, Decl(discriminantPropertyCheck.ts, 70, 21))
+
+                inst.value.toExponential;
+>inst.value.toExponential : Symbol(Number.toExponential, Decl(lib.es5.d.ts, --, --))
+>inst.value : Symbol(NumType.value, Decl(discriminantPropertyCheck.ts, 81, 20))
+>inst : Symbol(inst, Decl(discriminantPropertyCheck.ts, 85, 15))
+>value : Symbol(NumType.value, Decl(discriminantPropertyCheck.ts, 81, 20))
+>toExponential : Symbol(Number.toExponential, Decl(lib.es5.d.ts, --, --))
+
+                break;
+            }
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/discriminantPropertyCheck.types b/tests/baselines/reference/discriminantPropertyCheck.types
index 9815433c09d37..4f34ceafc4385 100644
--- a/tests/baselines/reference/discriminantPropertyCheck.types
+++ b/tests/baselines/reference/discriminantPropertyCheck.types
@@ -232,3 +232,81 @@ function foo6(x: Item) {
 >length : number
     }
 }
+
+// Repro from #27493
+
+enum Types { Str = 1, Num = 2 }
+>Types : Types
+>Str : Types.Str
+>1 : 1
+>Num : Types.Num
+>2 : 2
+
+type Instance = StrType | NumType;
+>Instance : Instance
+
+interface StrType {
+    type: Types.Str;
+>type : Types.Str
+>Types : any
+
+    value: string;
+>value : string
+
+    length: number;
+>length : number
+}
+
+interface NumType {
+    type: Types.Num;
+>type : Types.Num
+>Types : any
+
+    value: number;
+>value : number
+}
+
+function func2(inst: Instance) {
+>func2 : (inst: Instance) => void
+>inst : Instance
+
+    while (true) {
+>true : true
+
+        switch (inst.type) {
+>inst.type : Types
+>inst : Instance
+>type : Types
+
+            case Types.Str: {
+>Types.Str : Types.Str
+>Types : typeof Types
+>Str : Types.Str
+
+                inst.value.length;
+>inst.value.length : number
+>inst.value : string
+>inst : StrType
+>value : string
+>length : number
+
+                break;
+            }
+            case Types.Num: {
+>Types.Num : Types.Num
+>Types : typeof Types
+>Num : Types.Num
+
+                inst.value.toExponential;
+>inst.value.toExponential : (fractionDigits?: number | undefined) => string
+>inst.value : number
+>inst : NumType
+>value : number
+>toExponential : (fractionDigits?: number | undefined) => string
+
+                break;
+            }
+        }
+    }
+}
+
diff --git a/tests/cases/compiler/discriminantPropertyCheck.ts b/tests/cases/compiler/discriminantPropertyCheck.ts
index e493f6bf77042..16fb847bdf019 100644
--- a/tests/cases/compiler/discriminantPropertyCheck.ts
+++ b/tests/cases/compiler/discriminantPropertyCheck.ts
@@ -66,4 +66,36 @@ function foo6(x: Item) {
     if (x.foo !== undefined && x.qux) {
         x.foo.length;  // Error, intervening discriminant guard
     }
-}
\ No newline at end of file
+}
+
+// Repro from #27493
+
+enum Types { Str = 1, Num = 2 }
+
+type Instance = StrType | NumType;
+
+interface StrType {
+    type: Types.Str;
+    value: string;
+    length: number;
+}
+
+interface NumType {
+    type: Types.Num;
+    value: number;
+}
+
+function func2(inst: Instance) {
+    while (true) {
+        switch (inst.type) {
+            case Types.Str: {
+                inst.value.length;
+                break;
+            }
+            case Types.Num: {
+                inst.value.toExponential;
+                break;
+            }
+        }
+    }
+}