diff --git a/libavformat/crc.c b/libavformat/crc.c
index 40eed53e1f..8be5e734e2 100644
--- a/libavformat/crc.c
+++ b/libavformat/crc.c
@@ -29,7 +29,7 @@ static int crc_write_header(struct AVFormatContext *s)
     CRCState *crc = s->priv_data;
 
     /* init CRC */
-    crc->crcval = av_adler32_update(0, NULL, 0);
+    crc->crcval = 1;
 
     return 0;
 }
diff --git a/libavutil/adler32.c b/libavutil/adler32.c
index 1d814b4561..84b432138e 100644
--- a/libavutil/adler32.c
+++ b/libavutil/adler32.c
@@ -11,21 +11,16 @@
 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
 
 #define DO1(buf)  {s1 += *buf++; s2 += s1;}
-#define DO2(buf)  DO1(buf); DO1(buf);
-#define DO4(buf)  DO2(buf); DO2(buf);
-#define DO8(buf)  DO4(buf); DO4(buf);
-#define DO16(buf) DO8(buf); DO8(buf);
+#define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
+#define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
 
 unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)
 {
     unsigned long s1 = adler & 0xffff;
     unsigned long s2 = (adler >> 16) & 0xffff;
-    int k;
-
-    if (buf == NULL) return 1L;
 
     while (len > 0) {
-        k = FFMIN(len, NMAX);
+        int k = FFMIN(len, NMAX);
         len -= k;
 #ifndef CONFIG_SMALL
         while (k >= 16) {