diff --git a/src/Rules/PHPUnit/CoversHelper.php b/src/Rules/PHPUnit/CoversHelper.php
index 792fcc1..66d6edf 100644
--- a/src/Rules/PHPUnit/CoversHelper.php
+++ b/src/Rules/PHPUnit/CoversHelper.php
@@ -71,6 +71,13 @@ public function processCovers(
 	{
 		$errors = [];
 		$covers = (string) $phpDocTag->value;
+
+		if ($covers === '') {
+			$errors[] = RuleErrorBuilder::message('@covers value does not specify anything.')->build();
+
+			return $errors;
+		}
+
 		$isMethod = strpos($covers, '::') !== false;
 		$fullName = $covers;
 
@@ -94,17 +101,12 @@ public function processCovers(
 					$fullName
 				))->build();
 			}
-		} else {
-			if ($covers === '') {
-				$errors[] = RuleErrorBuilder::message('@covers value does not specify anything.')->build();
-
-				return $errors;
-			}
-
-			if (!isset($method) && $this->reflectionProvider->hasFunction(new Name($covers, []), null)) {
-				return $errors;
-			}
+		} elseif (isset($method) && $this->reflectionProvider->hasFunction(new Name($method, []), null)) {
+			return $errors;
+		} elseif (!isset($method) && $this->reflectionProvider->hasFunction(new Name($className, []), null)) {
+			return $errors;
 
+		} else {
 			$error = RuleErrorBuilder::message(sprintf(
 				'@covers value %s references an invalid %s.',
 				$fullName,
diff --git a/tests/Rules/PHPUnit/data/class-coverage.php b/tests/Rules/PHPUnit/data/class-coverage.php
index 35af204..2d4e0ef 100644
--- a/tests/Rules/PHPUnit/data/class-coverage.php
+++ b/tests/Rules/PHPUnit/data/class-coverage.php
@@ -50,3 +50,10 @@ class CoversNothing extends \PHPUnit\Framework\TestCase
 class CoversNotFullyQualified extends \PHPUnit\Framework\TestCase
 {
 }
+
+/**
+ * @covers ::str_replace
+ */
+class CoversGlobalFunction extends \PHPUnit\Framework\TestCase
+{
+}