diff --git a/libguile/read.c b/libguile/read.c
index ff507354d..17c0534c4 100644
--- a/libguile/read.c
+++ b/libguile/read.c
@@ -582,12 +582,21 @@ scm_read_mixed_case_symbol (int chr, SCM port)
 
   if (scm_is_pair (str))
     {
+      size_t len;
+
       str = scm_string_concatenate (scm_reverse_x (str, SCM_EOL));
-      result = scm_string_to_symbol (str);
+      len = scm_c_string_length (str);
 
       /* Per SRFI-88, `:' alone is an identifier, not a keyword.  */
-      if (postfix && ends_with_colon && (scm_c_string_length (result) > 1))
-	result = scm_symbol_to_keyword (result);
+      if (postfix && ends_with_colon && (len > 1))
+	{
+	  /* Strip off colon.  */
+	  str = scm_c_substring (str, 0, len-1);
+	  result = scm_string_to_symbol (str);
+	  result = scm_symbol_to_keyword (result);
+	}
+      else
+	result = scm_string_to_symbol (str);
     }
   else
     {
diff --git a/test-suite/tests/reader.test b/test-suite/tests/reader.test
index b068c716d..0b6f9a468 100644
--- a/test-suite/tests/reader.test
+++ b/test-suite/tests/reader.test
@@ -165,6 +165,11 @@
          (with-read-options '(keywords postfix)
            (lambda ()
              (read-string "keyword:")))))
+  (pass-if "long postfix keywords"
+    (eq? #:keyword0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789
+         (with-read-options '(keywords postfix)
+           (lambda ()
+             (read-string "keyword0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789:")))))
   (pass-if "`:' is not a postfix keyword (per SRFI-88)"
     (eq? ':
          (with-read-options '(keywords postfix)