diff --git a/src/Type/Constant/ConstantArrayType.php b/src/Type/Constant/ConstantArrayType.php
index ba30e4f5fe..ac91966025 100644
--- a/src/Type/Constant/ConstantArrayType.php
+++ b/src/Type/Constant/ConstantArrayType.php
@@ -1019,6 +1019,9 @@ public function sliceArray(Type $offsetType, Type $lengthType, TrinaryLogic $pre
 	public function spliceArray(Type $offsetType, Type $lengthType, Type $replacementType): Type
 	{
 		$keyTypesCount = count($this->keyTypes);
+		if ($keyTypesCount === 0) {
+			return $this;
+		}
 
 		$offset = $offsetType instanceof ConstantIntegerType ? $offsetType->getValue() : null;
 
diff --git a/tests/PHPStan/Analyser/AnalyserIntegrationTest.php b/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
index 0a80bdf1c7..898add9bcf 100644
--- a/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
+++ b/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
@@ -1493,6 +1493,13 @@ public function testBug12095(): void
 		$this->assertNoErrors($errors);
 	}
 
+	public function testBug13279(): void
+	{
+		$errors = $this->runAnalyse(__DIR__ . '/data/bug-13279.php');
+		$this->assertCount(1, $errors);
+		$this->assertSame('Parameter #2 $offset of function array_splice expects int, string given.', $errors[0]->getMessage());
+	}
+
 	/**
 	 * @param string[]|null $allAnalysedFiles
 	 * @return Error[]
diff --git a/tests/PHPStan/Analyser/data/bug-13279.php b/tests/PHPStan/Analyser/data/bug-13279.php
new file mode 100644
index 0000000000..feb687a3ed
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/bug-13279.php
@@ -0,0 +1,18 @@
+<?php declare(strict_types = 1);
+
+namespace Bug13279;
+
+class ReproduceMe
+{
+	public function crashIt(string $addMe = ''): string
+	{
+		$arg = [];
+		if ($addMe !== '') {
+			$arg[] = $addMe;
+		}
+
+		array_splice($arg, 'extra', 1);
+
+		return implode(' ', $arg);
+	}
+}