--- a/gdb/testsuite/gdb.base/dprintf.exp
+++ b/gdb/testsuite/gdb.base/dprintf.exp
@@ -131,6 +131,11 @@ if $target_can_dprintf {
 	"\[\r\n\]\tbreakpoint already hit 2 times"
 	"\[\r\n\]        agent-printf \"arg=%d, g=%d\\\\n\", arg, g"
     }
+
+    # Test unsupport commands.
+    gdb_test "dprintf $dp_location1,\"%s\\n\", \"test\"" "Dprintf .*"
+    gdb_test "continue" ".*Unsupported operator OP_STRING .* in expression.*" \
+      "3rd dprintf, agent"
 }
 
 gdb_test "set dprintf-style foobar" "Undefined item: \"foobar\"." \