diff --git a/src/Type/Php/TrimFunctionDynamicReturnTypeExtension.php b/src/Type/Php/TrimFunctionDynamicReturnTypeExtension.php
index 4a88a6616f0..f1d3e7fdf0b 100644
--- a/src/Type/Php/TrimFunctionDynamicReturnTypeExtension.php
+++ b/src/Type/Php/TrimFunctionDynamicReturnTypeExtension.php
@@ -71,7 +71,7 @@ public function getTypeFromFunctionCall(
 				if (count($stringConstantStrings) > 0) {
 					foreach ($stringConstantStrings as $stringConstantString) {
 						$result[] = new ConstantStringType(
-							$functionName === 'rtrim'
+							in_array($functionName, ['rtrim', 'chop'], true)
 								? rtrim($stringConstantString->getValue(), $trimConstantString->getValue())
 								: trim($stringConstantString->getValue(), $trimConstantString->getValue()),
 							true,
diff --git a/tests/PHPStan/Analyser/nsrt/bug-15684.php b/tests/PHPStan/Analyser/nsrt/bug-15684.php
new file mode 100644
index 00000000000..6ebb65d56f7
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-15684.php
@@ -0,0 +1,13 @@
+<?php declare(strict_types = 1);
+
+namespace Bug15684;
+
+use function PHPStan\Testing\assertType;
+
+function doFoo(): void
+{
+	assertType("' a'", chop(' a ', ' '));
+	assertType("'yax'", chop('yax', 'y'));
+	assertType("' a'", rtrim(' a ', ' '));
+	assertType('true', chop(' a ', ' ') === ' a');
+}