diff --git a/darkhttpd.c b/darkhttpd.c
index a59a90c..f932b3f 100644
--- a/darkhttpd.c
+++ b/darkhttpd.c
@@ -314,7 +314,8 @@ static const char *default_extension_map[] = {
     NULL
 };
 
-static const char default_mimetype[] = "application/octet-stream";
+static const char octet_stream[] = "application/octet-stream";
+static const char *default_mimetype = octet_stream;
 
 /* Prototypes. */
 static void poll_recv_request(struct connection *conn);
@@ -891,6 +892,9 @@ static void usage(const char *argv0) {
     "\t\tDo not serve listing if directory is requested.\n\n");
     printf("\t--mimetypes filename (optional)\n"
     "\t\tParses specified file for extension-MIME associations.\n\n");
+    printf("\t--default-mimetype string (optional, default: %s)\n"
+    "\t\tFiles with unknown extensions are served as this mimetype.\n\n",
+        octet_stream);
     printf("\t--uid uid/uname, --gid gid/gname (default: don't privdrop)\n"
     "\t\tDrops privileges to given uid:gid after initialization.\n\n");
     printf("\t--pidfile filename (default: no pidfile)\n"
@@ -1008,6 +1012,11 @@ static void parse_commandline(const int argc, char *argv[]) {
                 errx(1, "missing filename after --mimetypes");
             parse_extension_map_file(argv[i]);
         }
+        else if (strcmp(argv[i], "--default-mimetype") == 0) {
+            if (++i >= argc)
+                errx(1, "missing string after --default-mimetype");
+            default_mimetype = argv[i];
+        }
         else if (strcmp(argv[i], "--uid") == 0) {
             struct passwd *p;
             if (++i >= argc)
diff --git a/devel/cover b/devel/cover
index 0551697..d4096a2 100755
--- a/devel/cover
+++ b/devel/cover
@@ -77,7 +77,9 @@ echo "test/this-gets-replaced  ap2" >> $DIR/mimemap
 echo "# this is a comment" >> $DIR/mimemap
 printf "test/type3\\tapp3\r\n" >> $DIR/mimemap
 echo "test/type2  ap2" >> $DIR/mimemap
-./a.out $DIR --port $PORT --mimetypes $DIR/mimemap >/dev/null &
+./a.out $DIR --port $PORT \
+  --mimetypes $DIR/mimemap \
+  --default-mimetype test/default >/dev/null &
 PID=$!
 kill -0 $PID || exit 1
 python test_mimemap.py
diff --git a/devel/test_mimemap.py b/devel/test_mimemap.py
index 20d3e34..35b0227 100755
--- a/devel/test_mimemap.py
+++ b/devel/test_mimemap.py
@@ -11,7 +11,7 @@ class TestMimemap(TestHelper):
         self.files = [ ("test-file.a1",    "test/type1"),
                        ("test-file.ap2",   "test/type2"),
                        ("test-file.app3",  "test/type3"),
-                       ("test-file.appp4", "application/octet-stream") ]
+                       ("test-file.appp4", "test/default") ]
         for fn, _ in self.files:
             open(WWWROOT + "/" + fn, "w").write(self.data)