diff --git a/doc/zzuf.1 b/doc/zzuf.1
index 64fe34e..ef73e31 100644
--- a/doc/zzuf.1
+++ b/doc/zzuf.1
@@ -95,8 +95,8 @@ Multiple \fB\-I\fR flags can be specified, in which case files matching any one
 of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
 .TP
 \fB\-M\fR, \fB\-\-md5\fR
-Instead of displaying the program's output, just print the MD5 digest of that
-output.
+Instead of displaying the program's standard output, just print the MD5 digest
+of that output. The standard error channel is left untouched.
 .TP
 \fB\-n\fR, \fB\-\-network\fR
 Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
diff --git a/src/zzuf.c b/src/zzuf.c
index 107fb12..eb2fa57 100644
--- a/src/zzuf.c
+++ b/src/zzuf.c
@@ -592,7 +592,7 @@ static void read_children(void)
             if(j != 0)
                 child_list[i].bytes += ret;
 
-            if(md5 && j > 0)
+            if(md5 && j == 2)
                 _zz_md5_add(child_list[i].ctx, buf, ret);
             else if(!quiet || j == 0)
                 write((j < 2) ? STDERR_FILENO : STDOUT_FILENO, buf, ret);