diff --git a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
index 756a3311e8c..fbf917f126d 100644
--- a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
@@ -518,7 +518,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substr)
     if (Value(int_start).is_negative_infinity())
         int_start = 0;
     if (int_start < 0)
-        int_start = max(size + (i32)int_start, 0);
+        int_start = max(size + int_start, 0);
 
     auto length = vm.argument(1);
 
diff --git a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.substr.js b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.substr.js
index d452643295d..9c0273f7624 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.substr.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.substr.js
@@ -4,6 +4,9 @@ test("basic functionality", () => {
     expect("".substr(1)).toBe("");
     expect("".substr()).toBe("");
     expect("".substr(-1)).toBe("");
+    expect("a".substr(-1)).toBe("a");
+    expect("a".substr(-2)).toBe("a");
+    expect("a".substr(-3)).toBe("a");
     expect("hello friends".substr()).toBe("hello friends");
     expect("hello friends".substr(1)).toBe("ello friends");
     expect("hello friends".substr(0, 5)).toBe("hello");