diff --git a/tests/visual_tests/compare.py b/tests/visual_tests/compare.py
index 18dfffc74..21a627d99 100644
--- a/tests/visual_tests/compare.py
+++ b/tests/visual_tests/compare.py
@@ -20,7 +20,11 @@ def compare_pixels(pixel1, pixel2):
 def compare(fn1, fn2):
     global errors
     im1 = Image.open(fn1)
-    im2 = Image.open(fn2)
+    try:
+        im2 = Image.open(fn2)
+    except IOError:
+        errors.append((fn1, None))
+        return -1
     diff = 0
     pixels = im1.size[0] * im1.size[1]
     im1 = im1.getdata()
@@ -38,6 +42,9 @@ def summary():
         print "-"*80
         print "Summary:"
         for error in errors:
-            print "%s failed: %d different pixels" % error
+            if (error[1] is None):
+                print "Could not verify %s: No reference image found!" % error[0]
+            else:
+                print "%s failed: %d different pixels" % error
         print "-"*80
         sys.exit(1)
diff --git a/tests/visual_tests/test.py b/tests/visual_tests/test.py
index 8a3cf78f0..5f2463f91 100755
--- a/tests/visual_tests/test.py
+++ b/tests/visual_tests/test.py
@@ -8,15 +8,26 @@ import os.path
 from compare import compare, summary
 
 dirname = os.path.dirname(sys.argv[0])
-
-widths = [ 800, 600, 400, 300, 250, 200, 150, 100]
-filenames = ["list", "simple"]
-filenames_one_width = ["simple-E", "simple-NE", "simple-NW", "simple-N",
-    "simple-SE", "simple-SW", "simple-S", "simple-W",
-    "formating-1", "formating-2", "formating-3", "formating-4",
-    "shieldsymbolizer-1", "expressionformat"]
+files = [
+    ("list", 800, 600, 400, 300, 250, 200, 150, 100),
+    ("simple", 800, 600, 400, 300, 250, 200, 150, 100),
+    ("simple-E", 500),
+    ("simple-NE", 500),
+    ("simple-NW", 500),
+    ("simple-N", 500),
+    ("simple-SE", 500),
+    ("simple-SW", 500),
+    ("simple-S", 500),
+    ("simple-W", 500),
+    ("formating-1", 500),
+    ("formating-2", 500),
+    ("formating-3", 500),
+    ("formating-4", 500),
+    ("shieldsymbolizer-1", 490, 495, 497, 498, 499, 500, 501, 502, 505, 510),
+    ("expressionformat", 500)]
 
 def render(filename, width):
+    width = int(width)
     m = mapnik.Map(width, 100)
     mapnik.load_map(m, os.path.join(dirname, "%s.xml" % filename), False)
     bbox = mapnik.Box2d(-0.05, -0.01, 0.95, 0.01)
@@ -32,18 +43,15 @@ def render(filename, width):
     print "Rendering style \"%s\" with width %d ... %s" % (filename, width, rms)
     return m
     
-if len(sys.argv) > 1:
-    filenames = []
-    filenames_one_width = sys.argv[1:]
+if len(sys.argv) == 2:
+    files = [(sys.argv[1], 500)]
+elif len(sys.argv) > 2:
+    files = [sys.argv[1:]]
     
-for filename in filenames:
-    for width in widths:
-        m = render(filename, width)
-    mapnik.save_map(m, "%s-out.xml" % filename)
-
-for filename in filenames_one_width:
-    m = render(filename, 500)
-    mapnik.save_map(m, "%s-out.xml" % filename)
+for f in files:
+    for width in f[1:]:
+        m = render(f[0], width)
+    mapnik.save_map(m, "%s-out.xml" % f[0])
 
 summary()