diff --git a/beets/util/__init__.py b/beets/util/__init__.py
index 5ea021bdd..e2d09c3ab 100644
--- a/beets/util/__init__.py
+++ b/beets/util/__init__.py
@@ -700,6 +700,7 @@ def command_output(cmd, shell=False):
         raise subprocess.CalledProcessError(
             returncode=proc.returncode,
             cmd=b' '.join(cmd),
+            output=stdout + stderr,
         )
     return stdout
 
diff --git a/beets/util/artresizer.py b/beets/util/artresizer.py
index 775679568..6ef7770f8 100644
--- a/beets/util/artresizer.py
+++ b/beets/util/artresizer.py
@@ -123,10 +123,11 @@ def im_getsize(path_in):
     try:
         out = util.command_output(cmd)
     except subprocess.CalledProcessError as exc:
-        log.warn(
-            'ImageMagick invocation failed when '
-            'getting size with command {}: {}',
-            cmd, exc
+        log.warn('ImageMagick size query failed')
+        log.debug(
+            '`convert` exited with (status {}) when '
+            'getting size with command {}:\n{}',
+            exc.returncode, cmd, exc.output.strip()
         )
         return
     try:
diff --git a/beetsplug/fetchart.py b/beetsplug/fetchart.py
index 333d29a89..1b2089b58 100644
--- a/beetsplug/fetchart.py
+++ b/beetsplug/fetchart.py
@@ -528,6 +528,7 @@ class FetchArtPlugin(plugins.BeetsPlugin, RequestMixin):
 
         # get_size returns None if no local imaging backend is available
         size = ArtResizer.shared.get_size(candidate)
+        self._log.debug('image size: {}', size)
 
         if not size:
             self._log.warning(u'Could not get size of image (please see '
@@ -536,12 +537,25 @@ class FetchArtPlugin(plugins.BeetsPlugin, RequestMixin):
                               u'`enforce_ratio` may be violated.')
             return CANDIDATE_EXACT
 
-        if (not self.minwidth or size[0] >= self.minwidth) and (
-                not self.enforce_ratio or size[0] == size[1]):
-            if not self.maxwidth or size[0] > self.maxwidth:
-                return CANDIDATE_DOWNSCALE
-            return CANDIDATE_EXACT
-        return CANDIDATE_BAD
+        # Check minimum size.
+        if self.minwidth and size[0] < self.minwidth:
+            self._log.debug('image too small ({} < {})',
+                            size[0], self.minwidth)
+            return CANDIDATE_BAD
+
+        # Check aspect ratio.
+        if self.enforce_ratio and size[0] != size[1]:
+            self._log.debug('image is not square ({} != {})',
+                            size[0], size[1])
+            return CANDIDATE_BAD
+
+        # Check maximum size.
+        if self.maxwidth and size[0] > self.maxwidth:
+            self._log.debug('image needs resizing ({} > {})',
+                            size[0], self.maxwidth)
+            return CANDIDATE_DOWNSCALE
+
+        return CANDIDATE_EXACT
 
     def art_for_album(self, album, paths, local_only=False):
         """Given an Album object, returns a path to downloaded art for the
diff --git a/test/test_util.py b/test/test_util.py
index 6dacb7f57..db68ed885 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -108,7 +108,7 @@ class UtilTest(unittest.TestCase):
     def test_command_output(self, mock_popen):
         def popen_fail(*args, **kwargs):
             m = Mock(returncode=1)
-            m.communicate.return_value = None, None
+            m.communicate.return_value = 'foo', 'bar'
             return m
 
         mock_popen.side_effect = popen_fail