2 files changed, 9 insertions, 2 deletions
diff --git a/ChangeLog b/ChangeLog
index b013dfe8..9a9419fc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2015-08-04  Kaz Kylheku  <kaz@kylheku.com>
 
+	* stream.c (string_out_put_string): Do not return nil when
+	buffer calculations overflow, but throw exception.
+
+2015-08-04  Kaz Kylheku  <kaz@kylheku.com>
+
 	Remove useless return values and checks.
 
 	* stream.c (vformat_align_pre, vformat_align_post): Change to void
diff --git a/stream.c b/stream.c
index f612cefb..cf1f5a96 100644
--- a/stream.c
+++ b/stream.c
@@ -1490,12 +1490,12 @@ static val string_out_put_string(val stream, val str)
     size_t required_size = len + so->fill + 1;
 
     if (required_size < len)
-      return nil;
+      goto oflow;
 
     while (so->size <= required_size) {
       so->size *= 2;
       if (so->size < old_size)
-        return nil;
+        goto oflow;
     }
 
     if (so->size != old_size)
@@ -1505,6 +1505,8 @@ static val string_out_put_string(val stream, val str)
     wmemcpy(so->buf + so->fill, s, len + 1);
     so->fill += len;
     return t;
+oflow:
+    uw_throw(error_s, lit("string output stream overflow"));
   }
 }