diff --git a/implementations/python/preserves/text.py b/implementations/python/preserves/text.py
index decaeee..57f61c8 100644
--- a/implementations/python/preserves/text.py
+++ b/implementations/python/preserves/text.py
@@ -221,7 +221,9 @@ class Parser(TextCodec):
     def read_string(self, delimiter):
         def u16_escape(acc):
             n1 = self.hexnum(4)
-            if n1 >= 0xd800 and n1 <= 0xdbff:
+            if n1 >= 0xd800 and n1 <= 0xdfff:
+                if n1 >= 0xdc00:
+                    raise DecodeError('Bad first half of surrogate pair')
                 ok = True
                 ok = ok and self.nextchar() == '\\'
                 ok = ok and self.nextchar() == 'u'
diff --git a/implementations/python/tests/samples.bin b/implementations/python/tests/samples.bin
index 8ea5e28..3ef5ecf 100644
Binary files a/implementations/python/tests/samples.bin and b/implementations/python/tests/samples.bin differ
diff --git a/implementations/python/tests/samples.pr b/implementations/python/tests/samples.pr
index f969455..4ebe8e6 100644
--- a/implementations/python/tests/samples.pr
+++ b/implementations/python/tests/samples.pr
@@ -184,6 +184,22 @@
   string3: <Test #x"b10568656c6c6f" "hello">
   string4: <Test #x"b1 14 616263e6b0b4e6b0b45c2f22080c0a0d0978797a" "abc\u6c34\u6C34\\/\"\b\f\n\r\txyz">
   string5: <Test #x"b104f09d849e" "\uD834\uDD1E">
+  string6: @"Short unicode escape" <ParseError "\"\\u6c\"">
+  string7: @"Short unicode escape" <ParseError "\"\\u6c3\"">
+  surrogatepair0str: @"Unmatched high surrogate" <ParseError "\"blah\\uD834\"">
+  surrogatepair1str: @"Unmatched low surrogate" <ParseError "\"\\uDD1Eblah\"">
+  surrogatepair2str: @"Unmatched high surrogate" <ParseError "\"blah\\uD834blah\"">
+  surrogatepair3str: @"Unmatched low surrogate" <ParseError "\"blah\\uDD1Eblah\"">
+  surrogatepair4str: @"Swapped surrogates" <ParseError "\"blah\\uDD1E\\uD834blah\"">
+  surrogatepair5str: @"Two high surrogates" <ParseError "\"blah\\uD834\\uD834blah\"">
+  surrogatepair6str: @"Two low surrogates" <ParseError "\"blah\\uDD1E\\uDD1Eblah\"">
+  surrogatepair0sym: @"Unmatched high surrogate" <ParseError "|blah\\uD834|">
+  surrogatepair1sym: @"Unmatched low surrogate" <ParseError "|\\uDD1Eblah|">
+  surrogatepair2sym: @"Unmatched high surrogate" <ParseError "|blah\\uD834blah|">
+  surrogatepair3sym: @"Unmatched low surrogate" <ParseError "|blah\\uDD1Eblah|">
+  surrogatepair4sym: @"Swapped surrogates" <ParseError "|blah\\uDD1E\\uD834blah|">
+  surrogatepair5sym: @"Two high surrogates" <ParseError "|blah\\uD834\\uD834blah|">
+  surrogatepair6sym: @"Two low surrogates" <ParseError "|blah\\uDD1E\\uDD1Eblah|">
   symbol0: <Test #x"b300" ||>
   symbol2: <Test #x"b30568656c6c6f" hello>
   symbol3: <Test #x"b305312d322d33" 1-2-3>
@@ -197,6 +213,7 @@
   symbol11: <Test #x"b3042d2d2d61" ---a>
   symbol12: <Test #x"b3042d2d2d31" ---1>
   symbol13: <Test #x"b3042b312e78" +1.x>
+  symbol14: <Test #x"b304f09d849e" |\uD834\uDD1E|>
   tag0: @"Unexpected end tag" <DecodeError #x"84">
   tag1: @"Invalid tag" <DecodeError #x"10">
   tag2: @"Invalid tag" <DecodeError #x"61b10110">
diff --git a/implementations/racket/preserves/preserves/read-text.rkt b/implementations/racket/preserves/preserves/read-text.rkt
index bbd0cf5..762cefa 100644
--- a/implementations/racket/preserves/preserves/read-text.rkt
+++ b/implementations/racket/preserves/preserves/read-text.rkt
@@ -177,16 +177,18 @@
                         (match in-port
                           [(px #px#"^[a-fA-F0-9]{4}" (list hexdigits))
                            (define n1 (string->number (bytes->string/utf-8 hexdigits) 16))
-                           (if (<= #xd800 n1 #xdfff) ;; surrogate pair first half
-                               (match in-port
-                                 [(px #px#"^\\\\u([a-fA-F0-9]{4})" (list _ hexdigits2))
-                                  (define n2 (string->number (bytes->string/utf-8 hexdigits2) 16))
-                                  (if (<= #xdc00 n2 #xdfff)
-                                      (+ (arithmetic-shift (- n1 #xd800) 10)
-                                         (- n2 #xdc00)
-                                         #x10000)
-                                      (parse-error "Bad second half of surrogate pair"))]
-                                 [_ (parse-error "Missing second half of surrogate pair")])
+                           (if (<= #xd800 n1 #xdfff) ;; surrogate pair
+                               (if (>= n1 #xdc00)
+                                   (parse-error "Bad first half of surrogate pair")
+                                   (match in-port
+                                     [(px #px#"^\\\\u([a-fA-F0-9]{4})" (list _ hexdigits2))
+                                      (define n2 (string->number (bytes->string/utf-8 hexdigits2) 16))
+                                      (if (<= #xdc00 n2 #xdfff)
+                                          (+ (arithmetic-shift (- n1 #xd800) 10)
+                                             (- n2 #xdc00)
+                                             #x10000)
+                                          (parse-error "Bad second half of surrogate pair"))]
+                                     [_ (parse-error "Missing second half of surrogate pair")]))
                                n1)]
                           [_ (parse-error "Bad string \\u escape")])))))
 
diff --git a/implementations/racket/preserves/preserves/tests/Makefile b/implementations/racket/preserves/preserves/tests/Makefile
new file mode 100644
index 0000000..9eca976
--- /dev/null
+++ b/implementations/racket/preserves/preserves/tests/Makefile
@@ -0,0 +1,3 @@
+test:
+	$(MAKE) -C ../.. update-test-data
+	raco test test-main.rkt
diff --git a/implementations/racket/preserves/preserves/tests/samples.pr b/implementations/racket/preserves/preserves/tests/samples.pr
index f969455..4ebe8e6 100644
--- a/implementations/racket/preserves/preserves/tests/samples.pr
+++ b/implementations/racket/preserves/preserves/tests/samples.pr
@@ -184,6 +184,22 @@
   string3: <Test #x"b10568656c6c6f" "hello">
   string4: <Test #x"b1 14 616263e6b0b4e6b0b45c2f22080c0a0d0978797a" "abc\u6c34\u6C34\\/\"\b\f\n\r\txyz">
   string5: <Test #x"b104f09d849e" "\uD834\uDD1E">
+  string6: @"Short unicode escape" <ParseError "\"\\u6c\"">
+  string7: @"Short unicode escape" <ParseError "\"\\u6c3\"">
+  surrogatepair0str: @"Unmatched high surrogate" <ParseError "\"blah\\uD834\"">
+  surrogatepair1str: @"Unmatched low surrogate" <ParseError "\"\\uDD1Eblah\"">
+  surrogatepair2str: @"Unmatched high surrogate" <ParseError "\"blah\\uD834blah\"">
+  surrogatepair3str: @"Unmatched low surrogate" <ParseError "\"blah\\uDD1Eblah\"">
+  surrogatepair4str: @"Swapped surrogates" <ParseError "\"blah\\uDD1E\\uD834blah\"">
+  surrogatepair5str: @"Two high surrogates" <ParseError "\"blah\\uD834\\uD834blah\"">
+  surrogatepair6str: @"Two low surrogates" <ParseError "\"blah\\uDD1E\\uDD1Eblah\"">
+  surrogatepair0sym: @"Unmatched high surrogate" <ParseError "|blah\\uD834|">
+  surrogatepair1sym: @"Unmatched low surrogate" <ParseError "|\\uDD1Eblah|">
+  surrogatepair2sym: @"Unmatched high surrogate" <ParseError "|blah\\uD834blah|">
+  surrogatepair3sym: @"Unmatched low surrogate" <ParseError "|blah\\uDD1Eblah|">
+  surrogatepair4sym: @"Swapped surrogates" <ParseError "|blah\\uDD1E\\uD834blah|">
+  surrogatepair5sym: @"Two high surrogates" <ParseError "|blah\\uD834\\uD834blah|">
+  surrogatepair6sym: @"Two low surrogates" <ParseError "|blah\\uDD1E\\uDD1Eblah|">
   symbol0: <Test #x"b300" ||>
   symbol2: <Test #x"b30568656c6c6f" hello>
   symbol3: <Test #x"b305312d322d33" 1-2-3>
@@ -197,6 +213,7 @@
   symbol11: <Test #x"b3042d2d2d61" ---a>
   symbol12: <Test #x"b3042d2d2d31" ---1>
   symbol13: <Test #x"b3042b312e78" +1.x>
+  symbol14: <Test #x"b304f09d849e" |\uD834\uDD1E|>
   tag0: @"Unexpected end tag" <DecodeError #x"84">
   tag1: @"Invalid tag" <DecodeError #x"10">
   tag2: @"Invalid tag" <DecodeError #x"61b10110">
diff --git a/tests/samples.bin b/tests/samples.bin
index 8ea5e28..3ef5ecf 100644
Binary files a/tests/samples.bin and b/tests/samples.bin differ
diff --git a/tests/samples.pr b/tests/samples.pr
index f969455..4ebe8e6 100644
--- a/tests/samples.pr
+++ b/tests/samples.pr
@@ -184,6 +184,22 @@
   string3: <Test #x"b10568656c6c6f" "hello">
   string4: <Test #x"b1 14 616263e6b0b4e6b0b45c2f22080c0a0d0978797a" "abc\u6c34\u6C34\\/\"\b\f\n\r\txyz">
   string5: <Test #x"b104f09d849e" "\uD834\uDD1E">
+  string6: @"Short unicode escape" <ParseError "\"\\u6c\"">
+  string7: @"Short unicode escape" <ParseError "\"\\u6c3\"">
+  surrogatepair0str: @"Unmatched high surrogate" <ParseError "\"blah\\uD834\"">
+  surrogatepair1str: @"Unmatched low surrogate" <ParseError "\"\\uDD1Eblah\"">
+  surrogatepair2str: @"Unmatched high surrogate" <ParseError "\"blah\\uD834blah\"">
+  surrogatepair3str: @"Unmatched low surrogate" <ParseError "\"blah\\uDD1Eblah\"">
+  surrogatepair4str: @"Swapped surrogates" <ParseError "\"blah\\uDD1E\\uD834blah\"">
+  surrogatepair5str: @"Two high surrogates" <ParseError "\"blah\\uD834\\uD834blah\"">
+  surrogatepair6str: @"Two low surrogates" <ParseError "\"blah\\uDD1E\\uDD1Eblah\"">
+  surrogatepair0sym: @"Unmatched high surrogate" <ParseError "|blah\\uD834|">
+  surrogatepair1sym: @"Unmatched low surrogate" <ParseError "|\\uDD1Eblah|">
+  surrogatepair2sym: @"Unmatched high surrogate" <ParseError "|blah\\uD834blah|">
+  surrogatepair3sym: @"Unmatched low surrogate" <ParseError "|blah\\uDD1Eblah|">
+  surrogatepair4sym: @"Swapped surrogates" <ParseError "|blah\\uDD1E\\uD834blah|">
+  surrogatepair5sym: @"Two high surrogates" <ParseError "|blah\\uD834\\uD834blah|">
+  surrogatepair6sym: @"Two low surrogates" <ParseError "|blah\\uDD1E\\uDD1Eblah|">
   symbol0: <Test #x"b300" ||>
   symbol2: <Test #x"b30568656c6c6f" hello>
   symbol3: <Test #x"b305312d322d33" 1-2-3>
@@ -197,6 +213,7 @@
   symbol11: <Test #x"b3042d2d2d61" ---a>
   symbol12: <Test #x"b3042d2d2d31" ---1>
   symbol13: <Test #x"b3042b312e78" +1.x>
+  symbol14: <Test #x"b304f09d849e" |\uD834\uDD1E|>
   tag0: @"Unexpected end tag" <DecodeError #x"84">
   tag1: @"Invalid tag" <DecodeError #x"10">
   tag2: @"Invalid tag" <DecodeError #x"61b10110">