diff --git a/src/load.c b/src/load.c
index 2c7b71e..894ee10 100644
--- a/src/load.c
+++ b/src/load.c
@@ -699,7 +699,7 @@ static json_t *parse_object(lex_t *lex, size_t flags, json_error_t *error)
         key = lex_steal_string(lex, &len);
         if(!key)
             return NULL;
-        if (memchr(key, len, '\0')) {
+        if (memchr(key, '\0', len)) {
             jsonp_free(key);
             error_set(error, lex, "NUL byte in object key not supported");
             goto error;
diff --git a/test/suites/invalid/null-byte-in-object-key/error b/test/suites/invalid/null-byte-in-object-key/error
new file mode 100644
index 0000000..3ec685b
--- /dev/null
+++ b/test/suites/invalid/null-byte-in-object-key/error
@@ -0,0 +1,2 @@
+1 15 15
+NUL byte in object key not supported near '"foo\u0000bar"'
diff --git a/test/suites/invalid/null-byte-in-object-key/input b/test/suites/invalid/null-byte-in-object-key/input
new file mode 100644
index 0000000..593f0f6
--- /dev/null
+++ b/test/suites/invalid/null-byte-in-object-key/input
@@ -0,0 +1 @@
+{"foo\u0000bar": 42}
\ No newline at end of file