diff --git a/.travis.yml b/.travis.yml
index 81b4009e8..f8e4e723e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -32,7 +32,7 @@ matrix:
       env: DB=SQLITE
 
     - php: 7.4snapshot
-      env: DB=SQLITE
+      env: DB=SQLITE INSTALL_PHPUNIT_FORK=1
 
     # CMS test
     - php: 5.5
@@ -58,6 +58,7 @@ before_script:
  - if ! [ $(phpenv version-name) = "5.3" ]; then printf "\n" | travis_retry pecl install imagick; fi
  - if [ $(phpenv version-name) = "5.3" ]; then printf "\n" | travis_retry pecl install imagick-3.3.0; fi
  - composer self-update || true
+ - if [ $INSTALL_PHPUNIT_FORK ]; then composer require --no-update --dev sminnee/phpunit-mock-objects:^3.4.7; fi
  - phpenv rehash
  - phpenv config-rm xdebug.ini || true
  - echo 'memory_limit = 3G' >> ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/travis.ini
diff --git a/composer.json b/composer.json
index 622079296..bf7a3bb3a 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^3 || ^4 || ^5"
-    },
+	},
     "extra": [],
     "autoload": {
         "psr-0": {
@@ -63,4 +63,4 @@
             "core/compat"
         ]
     }
-}
\ No newline at end of file
+}
diff --git a/filesystem/GD.php b/filesystem/GD.php
index 4b863c712..488b8b067 100644
--- a/filesystem/GD.php
+++ b/filesystem/GD.php
@@ -140,7 +140,11 @@ class GDBackend extends SS_Object implements Image_Backend {
 		$bytesPerPixel = $bits * $channels;
 
 		// width * height * bytes per pixel
-		$memoryRequired = $imageInfo[0] * $imageInfo[1] * $bytesPerPixel;
+		if ($imageInfo) {
+			$memoryRequired = $imageInfo[0] * $imageInfo[1] * $bytesPerPixel;
+		} else {
+			$memoryRequired = 0;
+		}
 
 		return $memoryRequired + memory_get_usage() < $limit;
 	}