diff --git a/dump1090.c b/dump1090.c
index 11e563d..187efa6 100644
--- a/dump1090.c
+++ b/dump1090.c
@@ -832,7 +832,7 @@ int main(int argc, char **argv) {
 #ifndef _WIN32
         } else if (!strcmp(argv[j], "--write-json") && more) {
             ++j;
-            Modes.json_path = malloc(strlen(argv[j]) + 11);
+            Modes.json_path = malloc(strlen(argv[j]) + 15);
             strcpy(Modes.json_path, argv[j]);
             strcat(Modes.json_path, "/aircraft.json");
         } else if (!strcmp(argv[j], "--write-json-every") && more) {
diff --git a/net_io.c b/net_io.c
index a5d1262..f896d73 100644
--- a/net_io.c
+++ b/net_io.c
@@ -734,6 +734,7 @@ void modesWriteJson(const char *path)
     int fd;
     int len = 0;
     char *content;
+    mode_t mask;
 
     snprintf(tmppath, PATH_MAX, "%s.XXXXXX", path);
     tmppath[PATH_MAX-1] = 0;
@@ -741,6 +742,10 @@ void modesWriteJson(const char *path)
     if (fd < 0)
         return;
     
+    mask = umask(0);
+    umask(mask);
+    fchmod(fd, 0644 & ~mask);
+
     content = aircraftsToJson(&len);
     if (write(fd, content, len) != len)
         goto error_1;