diff --git a/Lib/os.py b/Lib/os.py
index 31002acb75b..2d1b29b57bf 100644
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -723,7 +723,7 @@ if not _exists("urandom"):
         """
         try:
             _urandomfd = open("/dev/urandom", O_RDONLY)
-        except:
+        except (OSError, IOError):
             raise NotImplementedError("/dev/urandom (or equivalent) not found")
         bytes = ""
         while len(bytes) < n:
diff --git a/Misc/NEWS b/Misc/NEWS
index 9eeeff8b4ab..b498cc31c39 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -61,6 +61,9 @@ Core and builtins
 Library
 -------
 
+- os.urandom no longer masks unrelated exceptions like SystemExit or
+  KeyboardInterrupt.
+
 - Bug #1525866: Don't copy directory stat times in 
   shutil.copytree on Windows