diff --git a/src/Psalm/Internal/Visitor/ReflectorVisitor.php b/src/Psalm/Internal/Visitor/ReflectorVisitor.php
index 6d2271e83..3282243bc 100644
--- a/src/Psalm/Internal/Visitor/ReflectorVisitor.php
+++ b/src/Psalm/Internal/Visitor/ReflectorVisitor.php
@@ -1052,6 +1052,11 @@ class ReflectorVisitor extends PhpParser\NodeVisitorAbstract implements PhpParse
 
                     $rules = \Psalm\Type\Algebra::getTruthsFromFormula($negated_formula);
 
+                    if (!$rules) {
+                        $var_assertions = [];
+                        break;
+                    }
+
                     foreach ($rules as $var_id => $rule) {
                         foreach ($rule as $rule_part) {
                             if (count($rule_part) > 1) {
diff --git a/tests/AssertTest.php b/tests/AssertTest.php
index 7fe876b1e..5a8baa5ad 100644
--- a/tests/AssertTest.php
+++ b/tests/AssertTest.php
@@ -124,6 +124,28 @@ class AssertTest extends TestCase
                         }
                     }',
             ],
+            'assertWithoutRedundantCondition' => [
+                '<?php
+                    /**
+                     * @param mixed $data
+                     * @throws \Exception
+                     */
+                    function assertIsLongString($data): void {
+                        if (!is_string($data)) {
+                            throw new Exception;
+                        }
+                        if (strlen($data) < 100) {
+                            throw new Exception;
+                        }
+                    }
+
+                    /**
+                     * @throws Exception
+                     */
+                    function f(string $s): void {
+                        assertIsLongString($s);
+                    }',
+            ],
             'assertInstanceOfBAnnotation' => [
                 '<?php
                     class A {}