diff --git a/test/libsolidity/syntaxTests/types/mapping/access_index_omitted.sol b/test/libsolidity/syntaxTests/types/mapping/access_index_omitted.sol
new file mode 100644
index 000000000..c08404cad
--- /dev/null
+++ b/test/libsolidity/syntaxTests/types/mapping/access_index_omitted.sol
@@ -0,0 +1,8 @@
+contract C {
+    mapping(uint => uint) m;
+    function f() public {
+        m[] = 3;
+    }
+}
+// ----
+// TypeError: (76-79): Index expression cannot be omitted.