diff --git a/modules/zlib/src/deflate.c b/modules/zlib/src/deflate.c
index 27f5ace8a..712d950d4 100644
--- a/modules/zlib/src/deflate.c
+++ b/modules/zlib/src/deflate.c
@@ -617,7 +617,8 @@ int ZEXPORT deflatePrime (strm, bits, value)
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
-    if (s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
+    if (bits < 0 || bits > 16 ||
+        s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
         return Z_BUF_ERROR;
     do {
         put = Buf_size - s->bi_valid;
diff --git a/security/nss/lib/zlib/deflate.c b/security/nss/lib/zlib/deflate.c
index 48dfcb139..725c7086a 100644
--- a/security/nss/lib/zlib/deflate.c
+++ b/security/nss/lib/zlib/deflate.c
@@ -586,7 +586,8 @@ int ZEXPORT deflatePrime (strm, bits, value)
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
-    if (s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
+    if (bits < 0 || bits > 16 ||
+        s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
         return Z_BUF_ERROR;
     do {
         put = Buf_size - s->bi_valid;