diff --git a/hledger-lib/Ledger/Dates.hs b/hledger-lib/Ledger/Dates.hs
index c62773cd1..eb7c054fa 100644
--- a/hledger-lib/Ledger/Dates.hs
+++ b/hledger-lib/Ledger/Dates.hs
@@ -262,11 +262,10 @@ ymd = do
   y <- many1 digit
   datesepchar
   m <- try (count 2 digit) <|> count 1 digit
-  guard (read m >= 1 && (read m <= 12))
-  -- when (read m < 1 || (read m > 12)) $ fail "bad month number specified"
+  when (read m < 1 || (read m > 12)) $ error $ "bad month number: " ++ m
   datesepchar
   d <- try (count 2 digit) <|> count 1 digit
-  when (read d < 1 || (read d > 31)) $ fail "bad day number specified"
+  when (read d < 1 || (read d > 31)) $ error $ "bad day number: " ++ d
   return $ (y,m,d)
 
 ym :: GenParser Char st SmartDate
diff --git a/tests/parse-dates.test b/tests/parse-dates.test
new file mode 100644
index 000000000..59dc4b6f4
--- /dev/null
+++ b/tests/parse-dates.test
@@ -0,0 +1,15 @@
+# dates with bad month or day numbers should be rejected
+-f- print
+<<<
+2010/31/12 x
+   a  1
+   b
+>>>2 /bad month number: 31/
+>>>= 1
+-f- print
+<<<
+2010/12/32 x
+   a  1
+   b
+>>>2 /bad day number: 32/
+>>>= 1