diff --git a/deflate.c b/deflate.c
index eed6ed8..12fbd5a 100644
--- a/deflate.c
+++ b/deflate.c
@@ -1,5 +1,5 @@
 /* deflate.c -- compress data using the deflation algorithm
- * Copyright (C) 1995-2011 Jean-loup Gailly and Mark Adler
+ * Copyright (C) 1995-2012 Jean-loup Gailly and Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -52,7 +52,7 @@
 #include "deflate.h"
 
 const char deflate_copyright[] =
-   " deflate 1.2.5.3 Copyright 1995-2011 Jean-loup Gailly and Mark Adler ";
+   " deflate 1.2.5.3 Copyright 1995-2012 Jean-loup Gailly and Mark Adler ";
 /*
   If you use the zlib library in a product, an acknowledgment is welcome
   in the documentation of your product. If for some reason you cannot
@@ -464,9 +464,23 @@ int ZEXPORT deflatePrime (strm, bits, value)
     int bits;
     int value;
 {
+    deflate_state *s;
+    int put;
+
     if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
-    strm->state->bi_valid = bits;
-    strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
+    s = strm->state;
+    if ((Bytef *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
+        return Z_BUF_ERROR;
+    do {
+        put = Buf_size - s->bi_valid;
+        if (put > bits)
+            put = bits;
+        s->bi_buf |= (ush)((value & ((1 << put) - 1)) << s->bi_valid);
+        s->bi_valid += put;
+        _tr_flush_bits(s);
+        value >>= put;
+        bits -= put;
+    } while (bits);
     return Z_OK;
 }
 
diff --git a/deflate.h b/deflate.h
index 442e14a..9284329 100644
--- a/deflate.h
+++ b/deflate.h
@@ -1,5 +1,5 @@
 /* deflate.h -- internal compression state
- * Copyright (C) 1995-2010 Jean-loup Gailly
+ * Copyright (C) 1995-2012 Jean-loup Gailly
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -48,6 +48,9 @@
 #define MAX_BITS 15
 /* All codes must not exceed MAX_BITS bits */
 
+#define Buf_size 16
+/* size of bit buffer in bi_buf */
+
 #define INIT_STATE    42
 #define EXTRA_STATE   69
 #define NAME_STATE    73
diff --git a/trees.c b/trees.c
index 56e9bb1..23156ab 100644
--- a/trees.c
+++ b/trees.c
@@ -1,5 +1,5 @@
 /* trees.c -- output deflated data using Huffman coding
- * Copyright (C) 1995-2010 Jean-loup Gailly
+ * Copyright (C) 1995-2012 Jean-loup Gailly
  * detect_data_type() function provided freely by Cosmin Truta, 2006
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
@@ -74,11 +74,6 @@ local const uch bl_order[BL_CODES]
  * probability, to avoid transmitting the lengths for unused bit length codes.
  */
 
-#define Buf_size (8 * 2*sizeof(char))
-/* Number of bits used within bi_buf. (bi_buf might be implemented on
- * more than 16 bits on some systems.)
- */
-
 /* ===========================================================================
  * Local data. These are initialized only once.
  */
diff --git a/zlib.h b/zlib.h
index 20e13db..8c2c56e 100644
--- a/zlib.h
+++ b/zlib.h
@@ -734,8 +734,9 @@ ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
    than or equal to 16, and that many of the least significant bits of value
    will be inserted in the output.
 
-     deflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
-   stream state was inconsistent.
+     deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
+   room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
+   source stream state was inconsistent.
 */
 
 ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,