diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ef279c287581a..e0dea081f67e8 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18501,8 +18501,8 @@ namespace ts {
             return restType && createArrayType(restType);
         }
 
-        function getEndLengthOfType(type: Type) {
-            return isTupleType(type) ? getTypeReferenceArity(type) - findLastIndex(type.target.elementFlags, f => !(f & ElementFlags.Required)) - 1 : 0;
+        function getEndLengthOfType(type: Type, flags: ElementFlags) {
+            return isTupleType(type) ? getTypeReferenceArity(type) - findLastIndex(type.target.elementFlags, f => !(f & flags)) - 1 : 0;
         }
 
         function getElementTypeOfSliceOfTupleType(type: TupleTypeReference, index: number, endSkipCount = 0, writing = false) {
@@ -19763,8 +19763,8 @@ namespace ts {
                             const sourceRestType = !isTupleType(source) || sourceArity > 0 && source.target.elementFlags[sourceArity - 1] & ElementFlags.Rest ?
                                 getTypeArguments(source)[sourceArity - 1] : undefined;
                             const endLength = !(target.target.combinedFlags & ElementFlags.Variable) ? 0 :
-                                sourceRestType ? getEndLengthOfType(target) :
-                                Math.min(getEndLengthOfType(source), getEndLengthOfType(target));
+                                sourceRestType ? getEndLengthOfType(target, ElementFlags.Required) :
+                                Math.min(getEndLengthOfType(source, ElementFlags.Required | ElementFlags.Optional), getEndLengthOfType(target, ElementFlags.Required));
                             const sourceEndLength = sourceRestType ? 0 : endLength;
                             // Infer between starting fixed elements.
                             for (let i = 0; i < startLength; i++) {
diff --git a/tests/baselines/reference/variadicTuples1.errors.txt b/tests/baselines/reference/variadicTuples1.errors.txt
index a50b0671fdeeb..863bc431f6f4b 100644
--- a/tests/baselines/reference/variadicTuples1.errors.txt
+++ b/tests/baselines/reference/variadicTuples1.errors.txt
@@ -473,4 +473,17 @@ tests/cases/conformance/types/tuple/variadicTuples1.ts(342,19): error TS2322: Ty
     
     declare const a: Desc<[string, number, boolean], object>;
     const b = a.bind("", 1);  // Desc<[boolean], object>
+    
+    // Repro from #39607
+    
+    declare function getUser(id: string, options?: { x?: string }): string;
+    
+    declare function getOrgUser(id: string, orgId: number, options?: { y?: number, z?: boolean }): void;
+    
+    function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U) {
+        return (...args: [...T]) => method(...args, {});
+    }
+    
+    callApi(getUser);
+    callApi(getOrgUser);
     
\ No newline at end of file
diff --git a/tests/baselines/reference/variadicTuples1.js b/tests/baselines/reference/variadicTuples1.js
index be8cf4838eea3..b75ffcb37009d 100644
--- a/tests/baselines/reference/variadicTuples1.js
+++ b/tests/baselines/reference/variadicTuples1.js
@@ -361,6 +361,19 @@ interface Desc<A extends unknown[], T> {
 
 declare const a: Desc<[string, number, boolean], object>;
 const b = a.bind("", 1);  // Desc<[boolean], object>
+
+// Repro from #39607
+
+declare function getUser(id: string, options?: { x?: string }): string;
+
+declare function getOrgUser(id: string, orgId: number, options?: { y?: number, z?: boolean }): void;
+
+function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U) {
+    return (...args: [...T]) => method(...args, {});
+}
+
+callApi(getUser);
+callApi(getOrgUser);
 
 
 //// [variadicTuples1.js]
@@ -568,6 +581,17 @@ function f23(args) {
     var v3 = f22(["foo", 42]); // [string]
 }
 var b = a.bind("", 1); // Desc<[boolean], object>
+function callApi(method) {
+    return function () {
+        var args = [];
+        for (var _i = 0; _i < arguments.length; _i++) {
+            args[_i] = arguments[_i];
+        }
+        return method.apply(void 0, __spreadArrays(args, [{}]));
+    };
+}
+callApi(getUser);
+callApi(getOrgUser);
 
 
 //// [variadicTuples1.d.ts]
@@ -720,3 +744,11 @@ interface Desc<A extends unknown[], T> {
 }
 declare const a: Desc<[string, number, boolean], object>;
 declare const b: Desc<[boolean], object>;
+declare function getUser(id: string, options?: {
+    x?: string;
+}): string;
+declare function getOrgUser(id: string, orgId: number, options?: {
+    y?: number;
+    z?: boolean;
+}): void;
+declare function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U): (...args_0: T) => U;
diff --git a/tests/baselines/reference/variadicTuples1.symbols b/tests/baselines/reference/variadicTuples1.symbols
index e7c9db73fc13f..c8dce6f67e6a7 100644
--- a/tests/baselines/reference/variadicTuples1.symbols
+++ b/tests/baselines/reference/variadicTuples1.symbols
@@ -1244,3 +1244,43 @@ const b = a.bind("", 1);  // Desc<[boolean], object>
 >a : Symbol(a, Decl(variadicTuples1.ts, 360, 13))
 >bind : Symbol(Desc.bind, Decl(variadicTuples1.ts, 356, 34))
 
+// Repro from #39607
+
+declare function getUser(id: string, options?: { x?: string }): string;
+>getUser : Symbol(getUser, Decl(variadicTuples1.ts, 361, 24))
+>id : Symbol(id, Decl(variadicTuples1.ts, 365, 25))
+>options : Symbol(options, Decl(variadicTuples1.ts, 365, 36))
+>x : Symbol(x, Decl(variadicTuples1.ts, 365, 48))
+
+declare function getOrgUser(id: string, orgId: number, options?: { y?: number, z?: boolean }): void;
+>getOrgUser : Symbol(getOrgUser, Decl(variadicTuples1.ts, 365, 71))
+>id : Symbol(id, Decl(variadicTuples1.ts, 367, 28))
+>orgId : Symbol(orgId, Decl(variadicTuples1.ts, 367, 39))
+>options : Symbol(options, Decl(variadicTuples1.ts, 367, 54))
+>y : Symbol(y, Decl(variadicTuples1.ts, 367, 66))
+>z : Symbol(z, Decl(variadicTuples1.ts, 367, 78))
+
+function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U) {
+>callApi : Symbol(callApi, Decl(variadicTuples1.ts, 367, 100))
+>T : Symbol(T, Decl(variadicTuples1.ts, 369, 17))
+>U : Symbol(U, Decl(variadicTuples1.ts, 369, 42))
+>method : Symbol(method, Decl(variadicTuples1.ts, 369, 53))
+>args : Symbol(args, Decl(variadicTuples1.ts, 369, 62))
+>T : Symbol(T, Decl(variadicTuples1.ts, 369, 17))
+>U : Symbol(U, Decl(variadicTuples1.ts, 369, 42))
+
+    return (...args: [...T]) => method(...args, {});
+>args : Symbol(args, Decl(variadicTuples1.ts, 370, 12))
+>T : Symbol(T, Decl(variadicTuples1.ts, 369, 17))
+>method : Symbol(method, Decl(variadicTuples1.ts, 369, 53))
+>args : Symbol(args, Decl(variadicTuples1.ts, 370, 12))
+}
+
+callApi(getUser);
+>callApi : Symbol(callApi, Decl(variadicTuples1.ts, 367, 100))
+>getUser : Symbol(getUser, Decl(variadicTuples1.ts, 361, 24))
+
+callApi(getOrgUser);
+>callApi : Symbol(callApi, Decl(variadicTuples1.ts, 367, 100))
+>getOrgUser : Symbol(getOrgUser, Decl(variadicTuples1.ts, 365, 71))
+
diff --git a/tests/baselines/reference/variadicTuples1.types b/tests/baselines/reference/variadicTuples1.types
index 6882761339374..dce37b089e51c 100644
--- a/tests/baselines/reference/variadicTuples1.types
+++ b/tests/baselines/reference/variadicTuples1.types
@@ -1279,3 +1279,44 @@ const b = a.bind("", 1);  // Desc<[boolean], object>
 >"" : ""
 >1 : 1
 
+// Repro from #39607
+
+declare function getUser(id: string, options?: { x?: string }): string;
+>getUser : (id: string, options?: { x?: string | undefined; } | undefined) => string
+>id : string
+>options : { x?: string | undefined; } | undefined
+>x : string | undefined
+
+declare function getOrgUser(id: string, orgId: number, options?: { y?: number, z?: boolean }): void;
+>getOrgUser : (id: string, orgId: number, options?: { y?: number | undefined; z?: boolean | undefined; } | undefined) => void
+>id : string
+>orgId : number
+>options : { y?: number | undefined; z?: boolean | undefined; } | undefined
+>y : number | undefined
+>z : boolean | undefined
+
+function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U) {
+>callApi : <T extends unknown[] = [], U = void>(method: (...args_0: T, args_1: object) => U) => (...args_0: T) => U
+>method : (...args_0: T, args_1: object) => U
+>args : [...T, object]
+
+    return (...args: [...T]) => method(...args, {});
+>(...args: [...T]) => method(...args, {}) : (...args_0: T) => U
+>args : [...T]
+>method(...args, {}) : U
+>method : (...args_0: T, args_1: object) => U
+>...args : T[number]
+>args : [...T]
+>{} : {}
+}
+
+callApi(getUser);
+>callApi(getUser) : (id: string) => string
+>callApi : <T extends unknown[] = [], U = void>(method: (...args_0: T, args_1: object) => U) => (...args_0: T) => U
+>getUser : (id: string, options?: { x?: string | undefined; } | undefined) => string
+
+callApi(getOrgUser);
+>callApi(getOrgUser) : (id: string, orgId: number) => void
+>callApi : <T extends unknown[] = [], U = void>(method: (...args_0: T, args_1: object) => U) => (...args_0: T) => U
+>getOrgUser : (id: string, orgId: number, options?: { y?: number | undefined; z?: boolean | undefined; } | undefined) => void
+
diff --git a/tests/cases/conformance/types/tuple/variadicTuples1.ts b/tests/cases/conformance/types/tuple/variadicTuples1.ts
index e6562f20ccc4c..2a34d06e2b0e1 100644
--- a/tests/cases/conformance/types/tuple/variadicTuples1.ts
+++ b/tests/cases/conformance/types/tuple/variadicTuples1.ts
@@ -363,3 +363,16 @@ interface Desc<A extends unknown[], T> {
 
 declare const a: Desc<[string, number, boolean], object>;
 const b = a.bind("", 1);  // Desc<[boolean], object>
+
+// Repro from #39607
+
+declare function getUser(id: string, options?: { x?: string }): string;
+
+declare function getOrgUser(id: string, orgId: number, options?: { y?: number, z?: boolean }): void;
+
+function callApi<T extends unknown[] = [], U = void>(method: (...args: [...T, object]) => U) {
+    return (...args: [...T]) => method(...args, {});
+}
+
+callApi(getUser);
+callApi(getOrgUser);