diff --git a/src/calibre/ebooks/oeb/reader.py b/src/calibre/ebooks/oeb/reader.py
index 5bb6b193f7..9e4b6238a0 100644
--- a/src/calibre/ebooks/oeb/reader.py
+++ b/src/calibre/ebooks/oeb/reader.py
@@ -188,8 +188,13 @@ class OEBReader(object):
                         href, _ = urldefrag(href)
                         if not href:
                             continue
-                        href = item.abshref(urlnormalize(href))
-                        scheme = urlparse(href).scheme
+                        try:
+                            href = item.abshref(urlnormalize(href))
+                            scheme = urlparse(href).scheme
+                        except:
+                            self.oeb.log.exception(
+                                'Skipping invalid href: %r'%href)
+                            continue
                         if not scheme and href not in known:
                             new.add(href)
                 elif item.media_type in OEB_STYLES:
diff --git a/src/calibre/ebooks/oeb/transforms/trimmanifest.py b/src/calibre/ebooks/oeb/transforms/trimmanifest.py
index 95501dbb9b..3d56f0ef3d 100644
--- a/src/calibre/ebooks/oeb/transforms/trimmanifest.py
+++ b/src/calibre/ebooks/oeb/transforms/trimmanifest.py
@@ -47,7 +47,10 @@ class ManifestTrimmer(object):
                    item.data is not None:
                     hrefs = [r[2] for r in iterlinks(item.data)]
                     for href in hrefs:
-                        href = item.abshref(urlnormalize(href))
+                        try:
+                            href = item.abshref(urlnormalize(href))
+                        except:
+                            continue
                         if href in oeb.manifest.hrefs:
                             found = oeb.manifest.hrefs[href]
                             if found not in used: