diff --git a/ext/standard/similar_text.php b/ext/standard/similar_text.php
index 1ad5347d339..7c4c44ced28 100644
--- a/ext/standard/similar_text.php
+++ b/ext/standard/similar_text.php
@@ -8,9 +8,11 @@
 use PHPCompiler\Func\Internal;
 use PHPCompiler\JIT\Builtin\StringSimilarText;
 use PHPCompiler\JIT\Context;
+use PHPCompiler\JIT\InternalStrictArg as JitInternalStrictArg;
 use PHPCompiler\JIT\JitStringBuiltinArg;
 use PHPCompiler\JIT\JitValueBox;
 use PHPCompiler\JIT\Variable as JITVariable;
+use PHPCompiler\VM\InternalStrictArg;
 use PHPLLVM\Builder;
 use PHPLLVM\Value;
 
@@ -30,8 +32,8 @@ public function execute(Frame $frame): void
         if ($argc < 2 || $argc > 3) {
             throw new \LogicException('similar_text() accepts two or three arguments in this compiler build');
         }
-        $s1 = VmString::coerceStringBuiltinArg($frame->calledArgs[0], 'similar_text', 0, 'string1');
-        $s2 = VmString::coerceStringBuiltinArg($frame->calledArgs[1], 'similar_text', 1, 'string2');
+        $s1 = self::vmStringArg($frame, 0, 'string1');
+        $s2 = self::vmStringArg($frame, 1, 'string2');
         if (3 === $argc) {
             $percent = 0.0;
             $sim = VmString::similar_text($s1, $s2, $percent);
@@ -55,8 +57,8 @@ public function call(Context $context, JITVariable ...$args): Value
             throw new \LogicException('similar_text() accepts two or three arguments in this compiler build');
         }
         StringSimilarText::ensureLinked($context);
-        $str0 = JitStringBuiltinArg::lower($context, $args[0], 'similar_text', 0, 'string1');
-        $str1 = JitStringBuiltinArg::lower($context, $args[1], 'similar_text', 1, 'string2');
+        $str0 = self::jitStringArg($context, $args[0], 1, 'string1');
+        $str1 = self::jitStringArg($context, $args[1], 2, 'string2');
         $p0 = $this->stringDataPtr($context, $str0);
         $p1 = $this->stringDataPtr($context, $str1);
         $fn = $context->lookupFunction('phpc_similar_text');
@@ -71,6 +73,37 @@ public function call(Context $context, JITVariable ...$args): Value
         return $sim;
     }
 
+    private static function vmStringArg(Frame $frame, int $argIndex, string $paramName): string
+    {
+        if (null !== $frame->parent && $frame->parent->block->strictTypes) {
+            return InternalStrictArg::requireString($frame, $argIndex, 'similar_text', $paramName)->toString();
+        }
+
+        return VmString::coerceStringBuiltinArg(
+            $frame->calledArgs[$argIndex],
+            'similar_text',
+            $argIndex,
+            $paramName
+        );
+    }
+
+    private static function jitStringArg(
+        Context $context,
+        JITVariable $arg,
+        int $argNumber,
+        string $paramName
+    ): Value {
+        JitInternalStrictArg::requireString($context, $arg, 'similar_text', $paramName, $argNumber);
+
+        return JitStringBuiltinArg::lower(
+            $context,
+            $arg,
+            'similar_text',
+            $argNumber - 1,
+            $paramName
+        );
+    }
+
     private function jitWriteSimilarityPercent(
         Context $context,
         Value $strData0,
diff --git a/test/compliance/SimilarTextJITTest.php b/test/compliance/SimilarTextJITTest.php
index 86bdeaf1abc..cb53aabfb39 100644
--- a/test/compliance/SimilarTextJITTest.php
+++ b/test/compliance/SimilarTextJITTest.php
@@ -25,6 +25,10 @@ public static function providePHPTests(): \Generator
             __DIR__.'/cases/stdlib/similar_text_coerce_jit.phpt',
             'similar_text_coerce_jit.phpt'
         );
+        yield 'similar_text_strict_types_jit.phpt' => self::parsePHPT(
+            __DIR__.'/cases/stdlib/similar_text_strict_types_jit.phpt',
+            'similar_text_strict_types_jit.phpt'
+        );
     }
 
     public function setUp(): void
diff --git a/test/compliance/SimilarTextVMTest.php b/test/compliance/SimilarTextVMTest.php
index 28f8ef0351a..ed0763aa58f 100644
--- a/test/compliance/SimilarTextVMTest.php
+++ b/test/compliance/SimilarTextVMTest.php
@@ -29,6 +29,10 @@ public static function providePHPTests(): \Generator
             __DIR__.'/cases/stdlib/similar_text_type_error.phpt',
             'similar_text_type_error.phpt'
         );
+        yield 'similar_text_strict_types.phpt' => self::parsePHPT(
+            __DIR__.'/cases/stdlib/similar_text_strict_types.phpt',
+            'similar_text_strict_types.phpt'
+        );
     }
 
     public function setUp(): void
diff --git a/test/compliance/cases/stdlib/similar_text_strict_types.phpt b/test/compliance/cases/stdlib/similar_text_strict_types.phpt
new file mode 100644
index 00000000000..34e7102926e
--- /dev/null
+++ b/test/compliance/cases/stdlib/similar_text_strict_types.phpt
@@ -0,0 +1,18 @@
+--TEST--
+stdlib similar_text() — strict call-site TypeError on int operands (#9519, ext/standard/string.c)
+--FILE--
+<?php
+declare(strict_types=1);
+try {
+    similar_text(123, '123');
+    echo "uncaught\n";
+} catch (Throwable $e) {
+    echo get_class($e), ': ', $e->getMessage(), "\n";
+}
+$p = 0.0;
+similar_text('hello', 'hello world', $p);
+var_export($p > 99.0);
+echo "\n";
+--EXPECT--
+TypeError: similar_text(): Argument #1 ($string1) must be of type string, int given
+false
diff --git a/test/compliance/cases/stdlib/similar_text_strict_types_jit.phpt b/test/compliance/cases/stdlib/similar_text_strict_types_jit.phpt
new file mode 100644
index 00000000000..8080ae8f493
--- /dev/null
+++ b/test/compliance/cases/stdlib/similar_text_strict_types_jit.phpt
@@ -0,0 +1,14 @@
+--TEST--
+stdlib similar_text() JIT — strict call-site TypeError on int operands (#9519)
+--JIT--
+--FILE--
+<?php
+declare(strict_types=1);
+try {
+    similar_text(123, '123');
+    echo "uncaught\n";
+} catch (Throwable $e) {
+    echo get_class($e), ': ', $e->getMessage(), "\n";
+}
+--EXPECT--
+TypeError: similar_text(): Argument #1 ($string1) must be of type string, int given
diff --git a/test/repro/issue_4543_similar_text.php b/test/repro/issue_4543_similar_text.php
index deaa066b2ba..4669b7824bb 100644
--- a/test/repro/issue_4543_similar_text.php
+++ b/test/repro/issue_4543_similar_text.php
@@ -1,10 +1,8 @@
 <?php
 declare(strict_types=1);
-// Zend coerces scalars to string
-echo similar_text(123, '123'), "\n";
-
+// Zend TypeErrors on int operands when strict_types=1 is in effect at the call site
 try {
-    similar_text([], 'x');
+    similar_text(123, '123');
 } catch (Throwable $e) {
     echo get_class($e), "\n";
 }