diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index fa70cc917a0..72dda7500f0 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -1051,12 +1051,24 @@ private function resolveType(Expr $node): Type
 			} else {
 				$right = $node->right;
 			}
+			$rightType = $this->getType($right);
+
+			$stringType = $rightType->toString();
+			if (
+				$node instanceof Node\Expr\BinaryOp\Mod
+				|| $node instanceof Node\Expr\AssignOp\Mod
+			) {
+				if ($stringType instanceof ConstantScalarType && $stringType->getValue() === '1') {
+					return new ConstantIntegerType(0);
+				}
+			}
+
+			$rightScalarTypes = TypeUtils::getConstantScalars($rightType->toNumber());
+			foreach ($rightScalarTypes as $scalarType) {
 
-			$rightTypes = TypeUtils::getConstantScalars($this->getType($right)->toNumber());
-			foreach ($rightTypes as $rightType) {
 				if (
-					$rightType->getValue() === 0
-					|| $rightType->getValue() === 0.0
+					$scalarType->getValue() === 0
+					|| $scalarType->getValue() === 0.0
 				) {
 					return new ErrorType();
 				}
@@ -1078,15 +1090,15 @@ private function resolveType(Expr $node): Type
 			}
 
 			$leftTypes = TypeUtils::getConstantScalars($this->getType($left));
-			$rightTypes = TypeUtils::getConstantScalars($this->getType($right));
+			$rightScalarTypes = TypeUtils::getConstantScalars($this->getType($right));
 
 			$leftTypesCount = count($leftTypes);
-			$rightTypesCount = count($rightTypes);
+			$rightTypesCount = count($rightScalarTypes);
 			if ($leftTypesCount > 0 && $rightTypesCount > 0) {
 				$resultTypes = [];
 				$generalize = $leftTypesCount * $rightTypesCount > self::CALCULATE_SCALARS_LIMIT;
 				foreach ($leftTypes as $leftType) {
-					foreach ($rightTypes as $rightType) {
+					foreach ($rightScalarTypes as $rightType) {
 						$resultType = $this->calculateFromScalars($node, $leftType, $rightType);
 						if ($generalize) {
 							$resultType = TypeUtils::generalizeType($resultType, GeneralizePrecision::lessSpecific());
diff --git a/tests/PHPStan/Analyser/data/modulo-operator.php b/tests/PHPStan/Analyser/data/modulo-operator.php
index 6e432eb2599..0f2395a28b4 100644
--- a/tests/PHPStan/Analyser/data/modulo-operator.php
+++ b/tests/PHPStan/Analyser/data/modulo-operator.php
@@ -45,4 +45,26 @@ function doBar(int $i, int $j, $p, $range, $zeroOrMore, $intConst, $unionRange,
 
 		assertType('int', $j % $i);
 	}
+
+	function moduleOne(int $i, float $f) {
+		assertType('0', true % '1');
+		assertType('0', false % '1');
+		assertType('0', null % '1');
+		assertType('0', -1 % '1');
+		assertType('0', 0 % '1');
+		assertType('0', 1 % '1');
+		assertType('0', '1' % '1');
+		assertType('0', 1.24 % '1');
+
+		assertType('0', $i % '1');
+		assertType('0', $f % '1');
+
+		assertType('0', $i % true);
+		assertType('0', $f % true);
+
+		$i %= '1';
+		$f %= '1';
+		assertType('0', $i);
+		assertType('0', $f);
+	}
 }