diff --git a/libraries/base/GHC/IO/Encoding.hs b/libraries/base/GHC/IO/Encoding.hs
index 014b61b8b02671f0ac1e7b981afef94445c34e47..76c7f55e02f66364b523c378e73a841c5812c5ec 100644
--- a/libraries/base/GHC/IO/Encoding.hs
+++ b/libraries/base/GHC/IO/Encoding.hs
@@ -235,14 +235,9 @@ mkTextEncoding e = case mb_coding_failure_mode of
         _             -> Nothing
 
 mkTextEncoding' :: CodingFailureMode -> String -> IO TextEncoding
-mkTextEncoding' cfm enc
-  -- First, specifically match on ASCII encodings directly using
-  -- several possible aliases (specified by RFC 1345 & co), which
-  -- allows us to handle ASCII conversions without iconv at all (see
-  -- trac #10298).
-  | any (== enc) ansiEncNames = return (UTF8.mkUTF8 cfm)
-  -- Otherwise, handle other encoding needs via iconv.
-  | otherwise = case [toUpper c | c <- enc, c /= '-'] of
+mkTextEncoding' cfm enc =
+  case [toUpper c | c <- enc, c /= '-'] of
+  -- UTF-8 and friends we can handle ourselves
     "UTF8"    -> return $ UTF8.mkUTF8 cfm
     "UTF16"   -> return $ UTF16.mkUTF16 cfm
     "UTF16LE" -> return $ UTF16.mkUTF16le cfm
@@ -254,13 +249,31 @@ mkTextEncoding' cfm enc
     'C':'P':n | [(cp,"")] <- reads n -> return $ CodePage.mkCodePageEncoding cfm cp
     _ -> unknownEncodingErr (enc ++ codingFailureModeSuffix cfm)
 #else
-    _ -> Iconv.mkIconvEncoding cfm enc
-#endif
+    -- Otherwise, handle other encoding needs via iconv.
+
+    -- Unfortunately there is no good way to determine whether iconv is actually
+    -- functional without telling it to do something.
+    _ -> do res <- Iconv.mkIconvEncoding cfm enc
+            let isAscii = any (== enc) ansiEncNames
+            case res of
+              Just e -> return e
+              -- At this point we know that we can't count on iconv to work
+              -- (see, for instance, Trac #10298). However, we still want to do
+              --  what we can to work with what we have. For instance, ASCII is
+              -- easy. We match on ASCII encodings directly using several
+              -- possible aliases (specified by RFC 1345 & Co) and for this use
+              -- the 'char8' encoding
+              Nothing
+                | isAscii   -> return char8
+                | otherwise ->
+                    unknownEncodingErr (enc ++ codingFailureModeSuffix cfm)
   where
     ansiEncNames = -- ASCII aliases
       [ "ANSI_X3.4-1968", "iso-ir-6", "ANSI_X3.4-1986", "ISO_646.irv:1991"
       , "US-ASCII", "us", "IBM367", "cp367", "csASCII", "ASCII", "ISO646-US"
       ]
+#endif
+
 
 latin1_encode :: CharBuffer -> Buffer Word8 -> IO (CharBuffer, Buffer Word8)
 latin1_encode input output = fmap (\(_why,input',output') -> (input',output')) $ Latin1.latin1_encode input output -- unchecked, used for char8
diff --git a/libraries/base/GHC/IO/Encoding/Iconv.hs b/libraries/base/GHC/IO/Encoding/Iconv.hs
index 89ca71e084add820e5b33359b65ae970f2f53c7e..061bd60c209a9868a846f0497160c243e7ee12dc 100644
--- a/libraries/base/GHC/IO/Encoding/Iconv.hs
+++ b/libraries/base/GHC/IO/Encoding/Iconv.hs
@@ -34,9 +34,10 @@ import GHC.Base () -- For build ordering
 #else
 
 import Foreign
-import Foreign.C
+import Foreign.C hiding (charIsRepresentable)
 import Data.Maybe
 import GHC.Base
+import GHC.Foreign (charIsRepresentable)
 import GHC.IO.Buffer
 import GHC.IO.Encoding.Failure
 import GHC.IO.Encoding.Types
@@ -96,15 +97,27 @@ char_shift :: Int
 char_shift | charSize == 2 = 1
            | otherwise     = 2
 
-iconvEncoding :: String -> IO TextEncoding
+iconvEncoding :: String -> IO (Maybe TextEncoding)
 iconvEncoding = mkIconvEncoding ErrorOnCodingFailure
 
-mkIconvEncoding :: CodingFailureMode -> String -> IO TextEncoding
+-- | Construct an iconv-based 'TextEncoding' for the given character set and
+-- 'CodingFailureMode'.
+--
+-- As iconv is missing in some minimal environments (e.g. #10298), this
+-- checks to ensure that iconv is working properly before returning the
+-- encoding, returning 'Nothing' if not.
+mkIconvEncoding :: CodingFailureMode -> String -> IO (Maybe TextEncoding)
 mkIconvEncoding cfm charset = do
-  return (TextEncoding {
-                textEncodingName = charset,
-                mkTextDecoder = newIConv raw_charset (haskellChar ++ suffix) (recoverDecode cfm) iconvDecode,
-                mkTextEncoder = newIConv haskellChar charset                 (recoverEncode cfm) iconvEncode})
+    let enc = TextEncoding {
+                  textEncodingName = charset,
+                  mkTextDecoder = newIConv raw_charset (haskellChar ++ suffix)
+                                           (recoverDecode cfm) iconvDecode,
+                  mkTextEncoder = newIConv haskellChar charset
+                                           (recoverEncode cfm) iconvEncode}
+    good <- charIsRepresentable enc 'a'
+    return $ if good
+               then Just enc
+               else Nothing
   where
     -- An annoying feature of GNU iconv is that the //PREFIXES only take
     -- effect when they appear on the tocode parameter to iconv_open:
diff --git a/libraries/base/GHC/TopHandler.hs b/libraries/base/GHC/TopHandler.hs
index e725196cdff1eea3a0ec1bb59c0cad731618c713..05c905f7c10bb7ec9001c90c1b17b9cd5a9ec52c 100644
--- a/libraries/base/GHC/TopHandler.hs
+++ b/libraries/base/GHC/TopHandler.hs
@@ -176,7 +176,12 @@ disasterHandler exit _ =
   withCAString "%s" $ \fmt ->
     withCAString msgStr $ \msg ->
       errorBelch fmt msg >> exit 1
-  where msgStr = "encountered an exception while trying to report an exception"
+  where
+    msgStr =
+        "encountered an exception while trying to report an exception." ++
+        "One possible reason for this is that we failed while trying to " ++
+        "encode an error message. Check that your locale is configured " ++
+        "properly."
 
 {- Note [Disaster with iconv]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/testsuite/tests/driver/Makefile b/testsuite/tests/driver/Makefile
index d5ce683842de1fbfdf3e8e83f1965e14872bd6ab..dc1238c005ae1e8bd1a1916d1c915e65f31b9783 100644
--- a/testsuite/tests/driver/Makefile
+++ b/testsuite/tests/driver/Makefile
@@ -550,6 +550,10 @@ T7130:
 T7563:
 	-"$(TEST_HC)" $(TEST_HC_OPTS_NO_RECOMP) -C T7563.hs
 
+# Below we set LC_ALL=C to request standard ASCII output in the resulting error
+# messages. Unfortunately, Mac OS X still uses a Unicode encoding even with
+# LC_ALL=C, so we expect these tests to fail there.
+
 .PHONY: T6037
 T6037:
 	-LC_ALL=C "$(TEST_HC)" $(TEST_HC_OPTS_NO_RECOMP) -c T6037.hs
diff --git a/testsuite/tests/driver/T2507.stderr b/testsuite/tests/driver/T2507.stderr
index eb0878f682d78e790f5bea23c5ccb73ab2587000..1a6e6f38f12301d81af6cbf12441e9fad0cc611a 100644
--- a/testsuite/tests/driver/T2507.stderr
+++ b/testsuite/tests/driver/T2507.stderr
@@ -1,5 +1,5 @@
 
 T2507.hs:5:7: error:
-    Couldn't match expected type ‘Int’ with actual type ‘()’
+    Couldn't match expected type `Int' with actual type `()'
     In the expression: ()
-    In an equation for ‘foo’: foo = ()
+    In an equation for `foo': foo = ()
diff --git a/testsuite/tests/driver/T8959a.stderr b/testsuite/tests/driver/T8959a.stderr
index defb34b853e15c49bb179ef86f00bcdc52f0d1c4..476b9ee0b1865263e0b0c38fe398c899985ae885 100644
--- a/testsuite/tests/driver/T8959a.stderr
+++ b/testsuite/tests/driver/T8959a.stderr
@@ -1,5 +1,5 @@
 
 T8959a.hs:5:7: error:
-    Couldn't match expected type ‘Int -> Int’ with actual type ‘()’
+    Couldn't match expected type `Int -> Int' with actual type `()'
     In the expression: ()
-    In an equation for ‘foo’: foo = ()
+    In an equation for `foo': foo = ()