diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 40385062b1b..f89e1f4939b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -17115,7 +17115,7 @@ namespace ts {
         function isUntypedFunctionCall(funcType: Type, apparentFuncType: Type, numCallSignatures: number, numConstructSignatures: number) {
             // We exclude union types because we may have a union of function types that happen to have no common signatures.
             return isTypeAny(funcType) || isTypeAny(apparentFuncType) && funcType.flags & TypeFlags.TypeParameter ||
-                !numCallSignatures && !numConstructSignatures && !(funcType.flags & (TypeFlags.Union | TypeFlags.Never)) && isTypeAssignableTo(funcType, globalFunctionType);
+                !numCallSignatures && !numConstructSignatures && !(apparentFuncType.flags & (TypeFlags.Union | TypeFlags.Never)) && isTypeAssignableTo(funcType, globalFunctionType);
         }
 
         function resolveNewExpression(node: NewExpression, candidatesOutArray: Signature[]): Signature {
diff --git a/tests/baselines/reference/functionCallOnConstrainedTypeVariable.errors.txt b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.errors.txt
new file mode 100644
index 00000000000..1ff56c7612f
--- /dev/null
+++ b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.errors.txt
@@ -0,0 +1,35 @@
+tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts(11,3): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts(15,3): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts(18,3): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts(19,3): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+
+
+==== tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts (4 errors) ====
+    // Repro from #20196
+    
+    type A = {
+      a: (x: number) => string
+    };
+    type B = {
+      a: (x: boolean) => string
+    };
+    
+    function call0(p: A | B) { 
+      p.a("s"); // Error
+      ~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+    }
+    
+    function callN<T extends A | B>(p: T) {
+      p.a("s"); // Error
+      ~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+      
+      var a: T["a"] = p.a;
+      a(""); // Error
+      ~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+      a("", "", "", ""); // Error
+      ~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type '((x: number) => string) | ((x: boolean) => string)' has no compatible call signatures.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/functionCallOnConstrainedTypeVariable.js b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.js
new file mode 100644
index 00000000000..34eab55aafe
--- /dev/null
+++ b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.js
@@ -0,0 +1,34 @@
+//// [functionCallOnConstrainedTypeVariable.ts]
+// Repro from #20196
+
+type A = {
+  a: (x: number) => string
+};
+type B = {
+  a: (x: boolean) => string
+};
+
+function call0(p: A | B) { 
+  p.a("s"); // Error
+}
+
+function callN<T extends A | B>(p: T) {
+  p.a("s"); // Error
+  
+  var a: T["a"] = p.a;
+  a(""); // Error
+  a("", "", "", ""); // Error
+}
+
+//// [functionCallOnConstrainedTypeVariable.js]
+"use strict";
+// Repro from #20196
+function call0(p) {
+    p.a("s"); // Error
+}
+function callN(p) {
+    p.a("s"); // Error
+    var a = p.a;
+    a(""); // Error
+    a("", "", "", ""); // Error
+}
diff --git a/tests/baselines/reference/functionCallOnConstrainedTypeVariable.symbols b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.symbols
new file mode 100644
index 00000000000..e5bdcff342b
--- /dev/null
+++ b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.symbols
@@ -0,0 +1,58 @@
+=== tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts ===
+// Repro from #20196
+
+type A = {
+>A : Symbol(A, Decl(functionCallOnConstrainedTypeVariable.ts, 0, 0))
+
+  a: (x: number) => string
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10))
+>x : Symbol(x, Decl(functionCallOnConstrainedTypeVariable.ts, 3, 6))
+
+};
+type B = {
+>B : Symbol(B, Decl(functionCallOnConstrainedTypeVariable.ts, 4, 2))
+
+  a: (x: boolean) => string
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+>x : Symbol(x, Decl(functionCallOnConstrainedTypeVariable.ts, 6, 6))
+
+};
+
+function call0(p: A | B) { 
+>call0 : Symbol(call0, Decl(functionCallOnConstrainedTypeVariable.ts, 7, 2))
+>p : Symbol(p, Decl(functionCallOnConstrainedTypeVariable.ts, 9, 15))
+>A : Symbol(A, Decl(functionCallOnConstrainedTypeVariable.ts, 0, 0))
+>B : Symbol(B, Decl(functionCallOnConstrainedTypeVariable.ts, 4, 2))
+
+  p.a("s"); // Error
+>p.a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10), Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+>p : Symbol(p, Decl(functionCallOnConstrainedTypeVariable.ts, 9, 15))
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10), Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+}
+
+function callN<T extends A | B>(p: T) {
+>callN : Symbol(callN, Decl(functionCallOnConstrainedTypeVariable.ts, 11, 1))
+>T : Symbol(T, Decl(functionCallOnConstrainedTypeVariable.ts, 13, 15))
+>A : Symbol(A, Decl(functionCallOnConstrainedTypeVariable.ts, 0, 0))
+>B : Symbol(B, Decl(functionCallOnConstrainedTypeVariable.ts, 4, 2))
+>p : Symbol(p, Decl(functionCallOnConstrainedTypeVariable.ts, 13, 32))
+>T : Symbol(T, Decl(functionCallOnConstrainedTypeVariable.ts, 13, 15))
+
+  p.a("s"); // Error
+>p.a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10), Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+>p : Symbol(p, Decl(functionCallOnConstrainedTypeVariable.ts, 13, 32))
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10), Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+  
+  var a: T["a"] = p.a;
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 16, 5))
+>T : Symbol(T, Decl(functionCallOnConstrainedTypeVariable.ts, 13, 15))
+>p.a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10), Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+>p : Symbol(p, Decl(functionCallOnConstrainedTypeVariable.ts, 13, 32))
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 2, 10), Decl(functionCallOnConstrainedTypeVariable.ts, 5, 10))
+
+  a(""); // Error
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 16, 5))
+
+  a("", "", "", ""); // Error
+>a : Symbol(a, Decl(functionCallOnConstrainedTypeVariable.ts, 16, 5))
+}
diff --git a/tests/baselines/reference/functionCallOnConstrainedTypeVariable.types b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.types
new file mode 100644
index 00000000000..9c6d349fac9
--- /dev/null
+++ b/tests/baselines/reference/functionCallOnConstrainedTypeVariable.types
@@ -0,0 +1,69 @@
+=== tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts ===
+// Repro from #20196
+
+type A = {
+>A : A
+
+  a: (x: number) => string
+>a : (x: number) => string
+>x : number
+
+};
+type B = {
+>B : B
+
+  a: (x: boolean) => string
+>a : (x: boolean) => string
+>x : boolean
+
+};
+
+function call0(p: A | B) { 
+>call0 : (p: A | B) => void
+>p : A | B
+>A : A
+>B : B
+
+  p.a("s"); // Error
+>p.a("s") : any
+>p.a : ((x: number) => string) | ((x: boolean) => string)
+>p : A | B
+>a : ((x: number) => string) | ((x: boolean) => string)
+>"s" : "s"
+}
+
+function callN<T extends A | B>(p: T) {
+>callN : <T extends A | B>(p: T) => void
+>T : T
+>A : A
+>B : B
+>p : T
+>T : T
+
+  p.a("s"); // Error
+>p.a("s") : any
+>p.a : ((x: number) => string) | ((x: boolean) => string)
+>p : T
+>a : ((x: number) => string) | ((x: boolean) => string)
+>"s" : "s"
+  
+  var a: T["a"] = p.a;
+>a : T["a"]
+>T : T
+>p.a : ((x: number) => string) | ((x: boolean) => string)
+>p : T
+>a : ((x: number) => string) | ((x: boolean) => string)
+
+  a(""); // Error
+>a("") : any
+>a : T["a"]
+>"" : ""
+
+  a("", "", "", ""); // Error
+>a("", "", "", "") : any
+>a : T["a"]
+>"" : ""
+>"" : ""
+>"" : ""
+>"" : ""
+}
diff --git a/tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts b/tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts
new file mode 100644
index 00000000000..8ceb578dc0a
--- /dev/null
+++ b/tests/cases/compiler/functionCallOnConstrainedTypeVariable.ts
@@ -0,0 +1,22 @@
+// @strict: true
+
+// Repro from #20196
+
+type A = {
+  a: (x: number) => string
+};
+type B = {
+  a: (x: boolean) => string
+};
+
+function call0(p: A | B) { 
+  p.a("s"); // Error
+}
+
+function callN<T extends A | B>(p: T) {
+  p.a("s"); // Error
+  
+  var a: T["a"] = p.a;
+  a(""); // Error
+  a("", "", "", ""); // Error
+}
\ No newline at end of file