diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 9a71a6a0277e8..f7c1c34c81c36 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -22165,7 +22165,8 @@ namespace ts {
             }
 
             function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
-                if (type.flags & (TypeFlags.Union | TypeFlags.Object)
+                if (type.flags & TypeFlags.Union
+                    || type.flags & TypeFlags.Object && declaredType !== type
                     || isThisTypeParameter(type)
                     || type.flags & TypeFlags.Intersection && every((type as IntersectionType).types, t => t.symbol !== globalThisSymbol)) {
                     const propName = escapeLeadingUnderscores(literal.text);
diff --git a/tests/baselines/reference/fixSignatureCaching.errors.txt b/tests/baselines/reference/fixSignatureCaching.errors.txt
index 4bb2276c3c554..d1c3ce6394fa8 100644
--- a/tests/baselines/reference/fixSignatureCaching.errors.txt
+++ b/tests/baselines/reference/fixSignatureCaching.errors.txt
@@ -3,7 +3,6 @@ tests/cases/conformance/fixSignatureCaching.ts(284,10): error TS2339: Property '
 tests/cases/conformance/fixSignatureCaching.ts(293,10): error TS2339: Property 'FALLBACK_PHONE' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(294,10): error TS2339: Property 'FALLBACK_TABLET' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(295,10): error TS2339: Property 'FALLBACK_MOBILE' does not exist on type '{}'.
-tests/cases/conformance/fixSignatureCaching.ts(301,17): error TS2339: Property 'isArray' does not exist on type 'never'.
 tests/cases/conformance/fixSignatureCaching.ts(330,74): error TS2339: Property 'mobileDetectRules' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(369,10): error TS2339: Property 'findMatch' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(387,10): error TS2339: Property 'findMatches' does not exist on type '{}'.
@@ -59,7 +58,7 @@ tests/cases/conformance/fixSignatureCaching.ts(981,16): error TS2304: Cannot fin
 tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property 'MobileDetect' does not exist on type 'Window & typeof globalThis'.
 
 
-==== tests/cases/conformance/fixSignatureCaching.ts (59 errors) ====
+==== tests/cases/conformance/fixSignatureCaching.ts (58 errors) ====
     // Repro from #10697
     
     (function (define, undefined) {
@@ -371,8 +370,6 @@ tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property '
         isArray = 'isArray' in Array
             ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }
             : Array.isArray;
-                    ~~~~~~~
-!!! error TS2339: Property 'isArray' does not exist on type 'never'.
     
         function equalIC(a, b) {
             return a != null && b != null && a.toLowerCase() === b.toLowerCase();
diff --git a/tests/baselines/reference/fixSignatureCaching.symbols b/tests/baselines/reference/fixSignatureCaching.symbols
index 97efe41ce1205..0ec1d2c63aae8 100644
--- a/tests/baselines/reference/fixSignatureCaching.symbols
+++ b/tests/baselines/reference/fixSignatureCaching.symbols
@@ -825,7 +825,9 @@ define(function () {
 >value : Symbol(value, Decl(fixSignatureCaching.ts, 299, 20))
 
         : Array.isArray;
+>Array.isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --))
 >Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --))
 
     function equalIC(a, b) {
 >equalIC : Symbol(equalIC, Decl(fixSignatureCaching.ts, 300, 24))
diff --git a/tests/baselines/reference/fixSignatureCaching.types b/tests/baselines/reference/fixSignatureCaching.types
index 8765e8fc310f4..7168cdf9fe238 100644
--- a/tests/baselines/reference/fixSignatureCaching.types
+++ b/tests/baselines/reference/fixSignatureCaching.types
@@ -1127,9 +1127,9 @@ define(function () {
 >'[object Array]' : "[object Array]"
 
     isArray = 'isArray' in Array
->isArray = 'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : any
+>isArray = 'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : (value: any) => boolean
 >isArray : any
->'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : any
+>'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : (value: any) => boolean
 >'isArray' in Array : boolean
 >'isArray' : "isArray"
 >Array : ArrayConstructor
@@ -1150,9 +1150,9 @@ define(function () {
 >'[object Array]' : "[object Array]"
 
         : Array.isArray;
->Array.isArray : any
->Array : never
->isArray : any
+>Array.isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
+>Array : ArrayConstructor
+>isArray : <T>(arg: {} | T) => arg is T extends readonly any[] ? unknown extends T ? never : readonly any[] : any[]
 
     function equalIC(a, b) {
 >equalIC : (a: any, b: any) => boolean
diff --git a/tests/baselines/reference/inKeywordTypeguard.errors.txt b/tests/baselines/reference/inKeywordTypeguard.errors.txt
index bb7d823d99d43..cfb2b090a7af5 100644
--- a/tests/baselines/reference/inKeywordTypeguard.errors.txt
+++ b/tests/baselines/reference/inKeywordTypeguard.errors.txt
@@ -165,6 +165,46 @@ tests/cases/compiler/inKeywordTypeguard.ts(94,26): error TS2339: Property 'a' do
             let n: never = x;
         }
     }
+    
+    // Repro from #38608
+    declare const error: Error;
+    if ('extra' in error) {
+        error // Still Error
+    } else {
+        error // Error
+    }
+    
+    function narrowsToNever(x: { l: number } | { r: number }) {
+        let v: number;
+        if ("l" in x) {
+            v = x.l;
+        }
+        else if ("r" in x) {
+            v = x.r;
+        }
+        else {
+            v = x
+        }
+        return v;
+    }
+    
+    type AOrB = { aProp: number } | { bProp: number };
+    declare function isAOrB(x: unknown): x is AOrB;
+    
+    declare var x: unknown;
+    if (isAOrB(x)) {
+        if ("aProp" in x) {
+            x.aProp;
+        }
+        else if ("bProp" in x) {
+            x.bProp;
+        }
+        // x is never because of the type predicate from unknown
+        else if ("cProp" in x) {
+            const _never: never = x;
+        }
+    }
+    
     function negativeIntersectionTest() {
         if ("ontouchstart" in window) {
             window.ontouchstart
diff --git a/tests/baselines/reference/inKeywordTypeguard.js b/tests/baselines/reference/inKeywordTypeguard.js
index d5a11599b64bb..e91a6ddf6e4d4 100644
--- a/tests/baselines/reference/inKeywordTypeguard.js
+++ b/tests/baselines/reference/inKeywordTypeguard.js
@@ -104,6 +104,46 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
         let n: never = x;
     }
 }
+
+// Repro from #38608
+declare const error: Error;
+if ('extra' in error) {
+    error // Still Error
+} else {
+    error // Error
+}
+
+function narrowsToNever(x: { l: number } | { r: number }) {
+    let v: number;
+    if ("l" in x) {
+        v = x.l;
+    }
+    else if ("r" in x) {
+        v = x.r;
+    }
+    else {
+        v = x
+    }
+    return v;
+}
+
+type AOrB = { aProp: number } | { bProp: number };
+declare function isAOrB(x: unknown): x is AOrB;
+
+declare var x: unknown;
+if (isAOrB(x)) {
+    if ("aProp" in x) {
+        x.aProp;
+    }
+    else if ("bProp" in x) {
+        x.bProp;
+    }
+    // x is never because of the type predicate from unknown
+    else if ("cProp" in x) {
+        const _never: never = x;
+    }
+}
+
 function negativeIntersectionTest() {
     if ("ontouchstart" in window) {
         window.ontouchstart
@@ -252,6 +292,37 @@ function positiveIntersectionTest(x) {
         var n = x;
     }
 }
+if ('extra' in error) {
+    error; // Still Error
+}
+else {
+    error; // Error
+}
+function narrowsToNever(x) {
+    var v;
+    if ("l" in x) {
+        v = x.l;
+    }
+    else if ("r" in x) {
+        v = x.r;
+    }
+    else {
+        v = x;
+    }
+    return v;
+}
+if (isAOrB(x)) {
+    if ("aProp" in x) {
+        x.aProp;
+    }
+    else if ("bProp" in x) {
+        x.bProp;
+    }
+    // x is never because of the type predicate from unknown
+    else if ("cProp" in x) {
+        var _never = x;
+    }
+}
 function negativeIntersectionTest() {
     if ("ontouchstart" in window) {
         window.ontouchstart;
diff --git a/tests/baselines/reference/inKeywordTypeguard.symbols b/tests/baselines/reference/inKeywordTypeguard.symbols
index 5ef75cbe25544..91d9c42597740 100644
--- a/tests/baselines/reference/inKeywordTypeguard.symbols
+++ b/tests/baselines/reference/inKeywordTypeguard.symbols
@@ -261,8 +261,105 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
 >x : Symbol(x, Decl(inKeywordTypeguard.ts, 98, 34))
     }
 }
+
+// Repro from #38608
+declare const error: Error;
+>error : Symbol(error, Decl(inKeywordTypeguard.ts, 107, 13))
+>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+if ('extra' in error) {
+>error : Symbol(error, Decl(inKeywordTypeguard.ts, 107, 13))
+
+    error // Still Error
+>error : Symbol(error, Decl(inKeywordTypeguard.ts, 107, 13))
+
+} else {
+    error // Error
+>error : Symbol(error, Decl(inKeywordTypeguard.ts, 107, 13))
+}
+
+function narrowsToNever(x: { l: number } | { r: number }) {
+>narrowsToNever : Symbol(narrowsToNever, Decl(inKeywordTypeguard.ts, 112, 1))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 114, 24))
+>l : Symbol(l, Decl(inKeywordTypeguard.ts, 114, 28))
+>r : Symbol(r, Decl(inKeywordTypeguard.ts, 114, 44))
+
+    let v: number;
+>v : Symbol(v, Decl(inKeywordTypeguard.ts, 115, 7))
+
+    if ("l" in x) {
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 114, 24))
+
+        v = x.l;
+>v : Symbol(v, Decl(inKeywordTypeguard.ts, 115, 7))
+>x.l : Symbol(l, Decl(inKeywordTypeguard.ts, 114, 28))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 114, 24))
+>l : Symbol(l, Decl(inKeywordTypeguard.ts, 114, 28))
+    }
+    else if ("r" in x) {
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 114, 24))
+
+        v = x.r;
+>v : Symbol(v, Decl(inKeywordTypeguard.ts, 115, 7))
+>x.r : Symbol(r, Decl(inKeywordTypeguard.ts, 114, 44))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 114, 24))
+>r : Symbol(r, Decl(inKeywordTypeguard.ts, 114, 44))
+    }
+    else {
+        v = x
+>v : Symbol(v, Decl(inKeywordTypeguard.ts, 115, 7))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 114, 24))
+    }
+    return v;
+>v : Symbol(v, Decl(inKeywordTypeguard.ts, 115, 7))
+}
+
+type AOrB = { aProp: number } | { bProp: number };
+>AOrB : Symbol(AOrB, Decl(inKeywordTypeguard.ts, 126, 1))
+>aProp : Symbol(aProp, Decl(inKeywordTypeguard.ts, 128, 13))
+>bProp : Symbol(bProp, Decl(inKeywordTypeguard.ts, 128, 33))
+
+declare function isAOrB(x: unknown): x is AOrB;
+>isAOrB : Symbol(isAOrB, Decl(inKeywordTypeguard.ts, 128, 50))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 129, 24))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 129, 24))
+>AOrB : Symbol(AOrB, Decl(inKeywordTypeguard.ts, 126, 1))
+
+declare var x: unknown;
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+
+if (isAOrB(x)) {
+>isAOrB : Symbol(isAOrB, Decl(inKeywordTypeguard.ts, 128, 50))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+
+    if ("aProp" in x) {
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+
+        x.aProp;
+>x.aProp : Symbol(aProp, Decl(inKeywordTypeguard.ts, 128, 13))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+>aProp : Symbol(aProp, Decl(inKeywordTypeguard.ts, 128, 13))
+    }
+    else if ("bProp" in x) {
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+
+        x.bProp;
+>x.bProp : Symbol(bProp, Decl(inKeywordTypeguard.ts, 128, 33))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+>bProp : Symbol(bProp, Decl(inKeywordTypeguard.ts, 128, 33))
+    }
+    // x is never because of the type predicate from unknown
+    else if ("cProp" in x) {
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+
+        const _never: never = x;
+>_never : Symbol(_never, Decl(inKeywordTypeguard.ts, 141, 13))
+>x : Symbol(x, Decl(inKeywordTypeguard.ts, 131, 11))
+    }
+}
+
 function negativeIntersectionTest() {
->negativeIntersectionTest : Symbol(negativeIntersectionTest, Decl(inKeywordTypeguard.ts, 104, 1))
+>negativeIntersectionTest : Symbol(negativeIntersectionTest, Decl(inKeywordTypeguard.ts, 143, 1))
 
     if ("ontouchstart" in window) {
 >window : Symbol(window, Decl(lib.dom.d.ts, --, --))
diff --git a/tests/baselines/reference/inKeywordTypeguard.types b/tests/baselines/reference/inKeywordTypeguard.types
index c5b735a51d9c1..e0956d838e2ec 100644
--- a/tests/baselines/reference/inKeywordTypeguard.types
+++ b/tests/baselines/reference/inKeywordTypeguard.types
@@ -321,6 +321,116 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
 >x : never
     }
 }
+
+// Repro from #38608
+declare const error: Error;
+>error : Error
+
+if ('extra' in error) {
+>'extra' in error : boolean
+>'extra' : "extra"
+>error : Error
+
+    error // Still Error
+>error : Error
+
+} else {
+    error // Error
+>error : Error
+}
+
+function narrowsToNever(x: { l: number } | { r: number }) {
+>narrowsToNever : (x: {    l: number;} | {    r: number;}) => number
+>x : { l: number; } | { r: number; }
+>l : number
+>r : number
+
+    let v: number;
+>v : number
+
+    if ("l" in x) {
+>"l" in x : boolean
+>"l" : "l"
+>x : { l: number; } | { r: number; }
+
+        v = x.l;
+>v = x.l : number
+>v : number
+>x.l : number
+>x : { l: number; }
+>l : number
+    }
+    else if ("r" in x) {
+>"r" in x : boolean
+>"r" : "r"
+>x : { r: number; }
+
+        v = x.r;
+>v = x.r : number
+>v : number
+>x.r : number
+>x : { r: number; }
+>r : number
+    }
+    else {
+        v = x
+>v = x : never
+>v : number
+>x : never
+    }
+    return v;
+>v : number
+}
+
+type AOrB = { aProp: number } | { bProp: number };
+>AOrB : AOrB
+>aProp : number
+>bProp : number
+
+declare function isAOrB(x: unknown): x is AOrB;
+>isAOrB : (x: unknown) => x is AOrB
+>x : unknown
+
+declare var x: unknown;
+>x : unknown
+
+if (isAOrB(x)) {
+>isAOrB(x) : boolean
+>isAOrB : (x: unknown) => x is AOrB
+>x : unknown
+
+    if ("aProp" in x) {
+>"aProp" in x : boolean
+>"aProp" : "aProp"
+>x : AOrB
+
+        x.aProp;
+>x.aProp : number
+>x : { aProp: number; }
+>aProp : number
+    }
+    else if ("bProp" in x) {
+>"bProp" in x : boolean
+>"bProp" : "bProp"
+>x : { bProp: number; }
+
+        x.bProp;
+>x.bProp : number
+>x : { bProp: number; }
+>bProp : number
+    }
+    // x is never because of the type predicate from unknown
+    else if ("cProp" in x) {
+>"cProp" in x : boolean
+>"cProp" : "cProp"
+>x : never
+
+        const _never: never = x;
+>_never : never
+>x : never
+    }
+}
+
 function negativeIntersectionTest() {
 >negativeIntersectionTest : () => void
 
diff --git a/tests/cases/compiler/inKeywordTypeguard.ts b/tests/cases/compiler/inKeywordTypeguard.ts
index d20404c949a86..e853d1935bee7 100644
--- a/tests/cases/compiler/inKeywordTypeguard.ts
+++ b/tests/cases/compiler/inKeywordTypeguard.ts
@@ -103,6 +103,46 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
         let n: never = x;
     }
 }
+
+// Repro from #38608
+declare const error: Error;
+if ('extra' in error) {
+    error // Still Error
+} else {
+    error // Error
+}
+
+function narrowsToNever(x: { l: number } | { r: number }) {
+    let v: number;
+    if ("l" in x) {
+        v = x.l;
+    }
+    else if ("r" in x) {
+        v = x.r;
+    }
+    else {
+        v = x
+    }
+    return v;
+}
+
+type AOrB = { aProp: number } | { bProp: number };
+declare function isAOrB(x: unknown): x is AOrB;
+
+declare var x: unknown;
+if (isAOrB(x)) {
+    if ("aProp" in x) {
+        x.aProp;
+    }
+    else if ("bProp" in x) {
+        x.bProp;
+    }
+    // x is never because of the type predicate from unknown
+    else if ("cProp" in x) {
+        const _never: never = x;
+    }
+}
+
 function negativeIntersectionTest() {
     if ("ontouchstart" in window) {
         window.ontouchstart