diff --git a/resources/functionMap.php b/resources/functionMap.php
index b157cf3da1..e95ce97992 100644
--- a/resources/functionMap.php
+++ b/resources/functionMap.php
@@ -9065,7 +9065,7 @@
 'rand\'1' => ['int'],
 'random_bytes' => ['string', 'length'=>'int'],
 'random_int' => ['int', 'min'=>'int', 'max'=>'int'],
-'range' => ['array', 'low'=>'mixed', 'high'=>'mixed', 'step='=>'int|float'],
+'range' => ['array', 'low'=>'int|float|string', 'high'=>'int|float|string', 'step='=>'int|float'],
 'RangeException::__clone' => ['void'],
 'RangeException::__construct' => ['void', 'message='=>'string', 'code='=>'int', 'previous='=>'(?Throwable)|(?RangeException)'],
 'RangeException::__toString' => ['string'],
diff --git a/src/Type/Constant/ConstantArrayTypeBuilder.php b/src/Type/Constant/ConstantArrayTypeBuilder.php
index 84fce75847..b5260b4164 100644
--- a/src/Type/Constant/ConstantArrayTypeBuilder.php
+++ b/src/Type/Constant/ConstantArrayTypeBuilder.php
@@ -5,6 +5,7 @@
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypeUtils;
 use function array_filter;
 
 class ConstantArrayTypeBuilder
@@ -97,7 +98,7 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $opt
 			return;
 		}
 
-		$this->keyTypes[] = $offsetType;
+		$this->keyTypes[] = TypeUtils::generalizeType($offsetType);
 		$this->valueTypes[] = $valueType;
 		$this->degradeToGeneralArray = true;
 	}
diff --git a/src/Type/Php/RangeFunctionReturnTypeExtension.php b/src/Type/Php/RangeFunctionReturnTypeExtension.php
index 65a7ab3236..91f0bc108f 100644
--- a/src/Type/Php/RangeFunctionReturnTypeExtension.php
+++ b/src/Type/Php/RangeFunctionReturnTypeExtension.php
@@ -7,11 +7,14 @@
 use PHPStan\Reflection\FunctionReflection;
 use PHPStan\Reflection\ParametersAcceptorSelector;
 use PHPStan\Type\ArrayType;
-use PHPStan\Type\Constant\ConstantArrayType;
+use PHPStan\Type\BenevolentUnionType;
+use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\Constant\ConstantFloatType;
 use PHPStan\Type\Constant\ConstantIntegerType;
+use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\FloatType;
 use PHPStan\Type\IntegerType;
+use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
 use PHPStan\Type\TypeUtils;
@@ -41,13 +44,13 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 
 		$startConstants = TypeUtils::getConstantScalars($startType);
 		foreach ($startConstants as $startConstant) {
-			if (!$startConstant instanceof ConstantIntegerType && !$startConstant instanceof ConstantFloatType) {
+			if (!$startConstant instanceof ConstantIntegerType && !$startConstant instanceof ConstantFloatType && !$startConstant instanceof ConstantStringType) {
 				continue;
 			}
 
 			$endConstants = TypeUtils::getConstantScalars($endType);
 			foreach ($endConstants as $endConstant) {
-				if (!$endConstant instanceof ConstantIntegerType && !$endConstant instanceof ConstantFloatType) {
+				if (!$endConstant instanceof ConstantIntegerType && !$endConstant instanceof ConstantFloatType && !$endConstant instanceof ConstantStringType) {
 					continue;
 				}
 
@@ -57,21 +60,16 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 						continue;
 					}
 
-					$rangeLength = (int) ceil(abs($startConstant->getValue() - $endConstant->getValue()) / $stepConstant->getValue()) + 1;
-					if ($rangeLength > self::RANGE_LENGTH_THRESHOLD) {
-						continue;
-					}
-
-					$keyTypes = [];
-					$valueTypes = [];
-
+					$arrayBuilder = ConstantArrayTypeBuilder::createEmpty();
 					$rangeValues = range($startConstant->getValue(), $endConstant->getValue(), $stepConstant->getValue());
-					foreach ($rangeValues as $key => $value) {
-						$keyTypes[] = new ConstantIntegerType($key);
-						$valueTypes[] = $scope->getTypeFromValue($value);
+					if (count($rangeValues) > self::RANGE_LENGTH_THRESHOLD) {
+						$arrayBuilder->degradeToGeneralArray();
+					}
+					foreach ($rangeValues as $value) {
+						$arrayBuilder->setOffsetValueType(null, $scope->getTypeFromValue($value));
 					}
 
-					$constantReturnTypes[] = new ConstantArrayType($keyTypes, $valueTypes, $rangeLength);
+					$constantReturnTypes[] = $arrayBuilder->getArray();
 				}
 			}
 		}
@@ -80,27 +78,31 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 			return TypeCombinator::union(...$constantReturnTypes);
 		}
 
-		$startType = TypeUtils::generalizeType($startType);
-		$endType = TypeUtils::generalizeType($endType);
-		$stepType = TypeUtils::generalizeType($stepType);
+		$argType = TypeCombinator::union($startType, $endType);
+		$isInteger = (new IntegerType())->isSuperTypeOf($argType)->yes();
+		$isStepInteger = (new IntegerType())->isSuperTypeOf($stepType)->yes();
 
-		if (
-			$startType instanceof IntegerType
-			&& $endType instanceof IntegerType
-			&& $stepType instanceof IntegerType
-		) {
+		if ($isInteger && $isStepInteger) {
 			return new ArrayType(new IntegerType(), new IntegerType());
 		}
 
-		if (
-			$startType instanceof FloatType
-			|| $endType instanceof FloatType
-			|| $stepType instanceof FloatType
-		) {
+		$isFloat = (new FloatType())->isSuperTypeOf($argType)->yes();
+		if ($isFloat) {
 			return new ArrayType(new IntegerType(), new FloatType());
 		}
 
-		return new ArrayType(new IntegerType(), new UnionType([new IntegerType(), new FloatType()]));
+		$numberType = new UnionType([new IntegerType(), new FloatType()]);
+		$isNumber = $numberType->isSuperTypeOf($argType)->yes();
+		if ($isNumber) {
+			return new ArrayType(new IntegerType(), $numberType);
+		}
+
+		$isString = (new StringType())->isSuperTypeOf($argType)->yes();
+		if ($isString) {
+			return new ArrayType(new IntegerType(), new StringType());
+		}
+
+		return new ArrayType(new IntegerType(), new BenevolentUnionType([new IntegerType(), new FloatType(), new StringType()]));
 	}
 
 }
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
index 0d257771b3..6a322d4a4c 100644
--- a/tests/PHPStan/Analyser/NodeScopeResolverTest.php
+++ b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -6076,15 +6076,15 @@ public function dataRangeFunction(): array
 				'range(2, 5, $integer)',
 			],
 			[
-				'array<int, float>',
+				'array<int, float|int>',
 				'range($float, 5, $integer)',
 			],
 			[
-				'array<int, float>',
+				'array<int, (float|int|string)>',
 				'range($float, $mixed, $integer)',
 			],
 			[
-				'array<int, float|int>',
+				'array<int, (float|int|string)>',
 				'range($integer, $mixed)',
 			],
 			[
@@ -10279,6 +10279,11 @@ public function dataBug3915(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3915.php');
 	}
 
+	public function dataBug2378(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/bug-2378.php');
+	}
+
 	/**
 	 * @param string $file
 	 * @return array<string, mixed[]>
@@ -10449,6 +10454,7 @@ private function gatherAssertTypes(string $file): array
 	 * @dataProvider dataPromotedProperties
 	 * @dataProvider dataNeverEarlyTerminates
 	 * @dataProvider dataBug3915
+	 * @dataProvider dataBug2378
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args
diff --git a/tests/PHPStan/Analyser/data/bug-2378.php b/tests/PHPStan/Analyser/data/bug-2378.php
new file mode 100644
index 0000000000..4e5dac9407
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/bug-2378.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Bug2375;
+
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+
+	public function doFoo(
+		$mixed,
+		int $int,
+		string $s,
+		float $f
+	): void
+	{
+		assertType('array(\'a\', \'b\', \'c\', \'d\')', range('a', 'd'));
+		assertType('array(\'a\', \'c\', \'e\', \'g\', \'i\')', range('a', 'i', 2));
+
+		assertType('array<int, string>', range($s, $s));
+	}
+
+}