diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3be17bfdaa6da..41164ff435e21 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -34167,7 +34167,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function hasEmptyObjectIntersection(type: Type): boolean {
-        return someType(type, t => t === unknownEmptyObjectType || !!(t.flags & TypeFlags.Intersection) && some((t as IntersectionType).types, isEmptyAnonymousObjectType));
+        return someType(type, t => t === unknownEmptyObjectType || !!(t.flags & TypeFlags.Intersection) && isEmptyAnonymousObjectType(getBaseConstraintOrType(t)));
     }
 
     function checkInExpression(left: Expression, right: Expression, leftType: Type, rightType: Type): Type {
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=false).errors.txt b/tests/baselines/reference/inKeywordTypeguard(strict=false).errors.txt
index 009acf38c2b18..7d8bd0bea9a4b 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=false).errors.txt
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=false).errors.txt
@@ -420,4 +420,16 @@ tests/cases/compiler/inKeywordTypeguard.ts(186,21): error TS2322: Type 'T' is no
     
     const checkIsTouchDevice = () =>
         "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+    
+    // Repro from #51501
+    
+    function isHTMLTable<T extends object | null>(table: T): boolean {
+        return !!table && 'html' in table;
+    }
+    
+    // Repro from #51549
+    
+    const f = <P extends object>(a: P & {}) => {
+        "foo" in a;
+    };
     
\ No newline at end of file
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=false).js b/tests/baselines/reference/inKeywordTypeguard(strict=false).js
index d254218557fa3..ae1ccbb43c5be 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=false).js
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=false).js
@@ -341,6 +341,18 @@ function foo<A>(value: A) {
 
 const checkIsTouchDevice = () =>
     "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+    return !!table && 'html' in table;
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+    "foo" in a;
+};
 
 
 //// [inKeywordTypeguard.js]
@@ -655,3 +667,11 @@ function foo(value) {
 }
 // Repro from #50954
 const checkIsTouchDevice = () => "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+// Repro from #51501
+function isHTMLTable(table) {
+    return !!table && 'html' in table;
+}
+// Repro from #51549
+const f = (a) => {
+    "foo" in a;
+};
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=false).symbols b/tests/baselines/reference/inKeywordTypeguard(strict=false).symbols
index c7ad966debf4d..9444bf3fc988c 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=false).symbols
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=false).symbols
@@ -853,3 +853,29 @@ const checkIsTouchDevice = () =>
 >window : Symbol(window, Decl(lib.dom.d.ts, --, --))
 >navigator : Symbol(navigator, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
 
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+>isHTMLTable : Symbol(isHTMLTable, Decl(inKeywordTypeguard.ts, 341, 71))
+>T : Symbol(T, Decl(inKeywordTypeguard.ts, 345, 21))
+>table : Symbol(table, Decl(inKeywordTypeguard.ts, 345, 46))
+>T : Symbol(T, Decl(inKeywordTypeguard.ts, 345, 21))
+
+    return !!table && 'html' in table;
+>table : Symbol(table, Decl(inKeywordTypeguard.ts, 345, 46))
+>table : Symbol(table, Decl(inKeywordTypeguard.ts, 345, 46))
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+>f : Symbol(f, Decl(inKeywordTypeguard.ts, 351, 5))
+>P : Symbol(P, Decl(inKeywordTypeguard.ts, 351, 11))
+>a : Symbol(a, Decl(inKeywordTypeguard.ts, 351, 29))
+>P : Symbol(P, Decl(inKeywordTypeguard.ts, 351, 11))
+
+    "foo" in a;
+>a : Symbol(a, Decl(inKeywordTypeguard.ts, 351, 29))
+
+};
+
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=false).types b/tests/baselines/reference/inKeywordTypeguard(strict=false).types
index 710206712629b..152eba6bda250 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=false).types
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=false).types
@@ -1056,3 +1056,34 @@ const checkIsTouchDevice = () =>
 >window : Window & typeof globalThis
 >navigator : Navigator
 
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+>isHTMLTable : <T extends object>(table: T) => boolean
+>null : null
+>table : T
+
+    return !!table && 'html' in table;
+>!!table && 'html' in table : boolean
+>!!table : boolean
+>!table : boolean
+>table : T
+>'html' in table : boolean
+>'html' : "html"
+>table : T
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+>f : <P extends object>(a: P & {}) => void
+><P extends object>(a: P & {}) => {    "foo" in a;} : <P extends object>(a: P & {}) => void
+>a : P & {}
+
+    "foo" in a;
+>"foo" in a : boolean
+>"foo" : "foo"
+>a : P & {}
+
+};
+
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=true).errors.txt b/tests/baselines/reference/inKeywordTypeguard(strict=true).errors.txt
index 1f11114fbd02c..d47a0718aac8a 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=true).errors.txt
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=true).errors.txt
@@ -440,4 +440,16 @@ tests/cases/compiler/inKeywordTypeguard.ts(186,21): error TS2638: Type 'NonNulla
     
     const checkIsTouchDevice = () =>
         "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+    
+    // Repro from #51501
+    
+    function isHTMLTable<T extends object | null>(table: T): boolean {
+        return !!table && 'html' in table;
+    }
+    
+    // Repro from #51549
+    
+    const f = <P extends object>(a: P & {}) => {
+        "foo" in a;
+    };
     
\ No newline at end of file
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=true).js b/tests/baselines/reference/inKeywordTypeguard(strict=true).js
index 9acc8ca7520e4..73b2cf77cae44 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=true).js
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=true).js
@@ -341,6 +341,18 @@ function foo<A>(value: A) {
 
 const checkIsTouchDevice = () =>
     "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+    return !!table && 'html' in table;
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+    "foo" in a;
+};
 
 
 //// [inKeywordTypeguard.js]
@@ -656,3 +668,11 @@ function foo(value) {
 }
 // Repro from #50954
 const checkIsTouchDevice = () => "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+// Repro from #51501
+function isHTMLTable(table) {
+    return !!table && 'html' in table;
+}
+// Repro from #51549
+const f = (a) => {
+    "foo" in a;
+};
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=true).symbols b/tests/baselines/reference/inKeywordTypeguard(strict=true).symbols
index c7ad966debf4d..9444bf3fc988c 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=true).symbols
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=true).symbols
@@ -853,3 +853,29 @@ const checkIsTouchDevice = () =>
 >window : Symbol(window, Decl(lib.dom.d.ts, --, --))
 >navigator : Symbol(navigator, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
 
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+>isHTMLTable : Symbol(isHTMLTable, Decl(inKeywordTypeguard.ts, 341, 71))
+>T : Symbol(T, Decl(inKeywordTypeguard.ts, 345, 21))
+>table : Symbol(table, Decl(inKeywordTypeguard.ts, 345, 46))
+>T : Symbol(T, Decl(inKeywordTypeguard.ts, 345, 21))
+
+    return !!table && 'html' in table;
+>table : Symbol(table, Decl(inKeywordTypeguard.ts, 345, 46))
+>table : Symbol(table, Decl(inKeywordTypeguard.ts, 345, 46))
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+>f : Symbol(f, Decl(inKeywordTypeguard.ts, 351, 5))
+>P : Symbol(P, Decl(inKeywordTypeguard.ts, 351, 11))
+>a : Symbol(a, Decl(inKeywordTypeguard.ts, 351, 29))
+>P : Symbol(P, Decl(inKeywordTypeguard.ts, 351, 11))
+
+    "foo" in a;
+>a : Symbol(a, Decl(inKeywordTypeguard.ts, 351, 29))
+
+};
+
diff --git a/tests/baselines/reference/inKeywordTypeguard(strict=true).types b/tests/baselines/reference/inKeywordTypeguard(strict=true).types
index 86da8b3e869cb..491c4858e543e 100644
--- a/tests/baselines/reference/inKeywordTypeguard(strict=true).types
+++ b/tests/baselines/reference/inKeywordTypeguard(strict=true).types
@@ -1056,3 +1056,34 @@ const checkIsTouchDevice = () =>
 >window : Window & typeof globalThis
 >navigator : Navigator
 
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+>isHTMLTable : <T extends object | null>(table: T) => boolean
+>null : null
+>table : T
+
+    return !!table && 'html' in table;
+>!!table && 'html' in table : boolean
+>!!table : boolean
+>!table : boolean
+>table : T
+>'html' in table : boolean
+>'html' : "html"
+>table : NonNullable<T>
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+>f : <P extends object>(a: P & {}) => void
+><P extends object>(a: P & {}) => {    "foo" in a;} : <P extends object>(a: P & {}) => void
+>a : P & {}
+
+    "foo" in a;
+>"foo" in a : boolean
+>"foo" : "foo"
+>a : P & {}
+
+};
+
diff --git a/tests/cases/compiler/inKeywordTypeguard.ts b/tests/cases/compiler/inKeywordTypeguard.ts
index 47266e55bd901..0c74dcded90ba 100644
--- a/tests/cases/compiler/inKeywordTypeguard.ts
+++ b/tests/cases/compiler/inKeywordTypeguard.ts
@@ -343,3 +343,15 @@ function foo<A>(value: A) {
 
 const checkIsTouchDevice = () =>
     "ontouchstart" in window || "msMaxTouchPoints" in window.navigator;
+
+// Repro from #51501
+
+function isHTMLTable<T extends object | null>(table: T): boolean {
+    return !!table && 'html' in table;
+}
+
+// Repro from #51549
+
+const f = <P extends object>(a: P & {}) => {
+    "foo" in a;
+};