diff --git a/river/command/filter.zig b/river/command/filter.zig
index f8f6143..6d6ac35 100644
--- a/river/command/filter.zig
+++ b/river/command/filter.zig
@@ -50,7 +50,7 @@ pub fn floatFilterAdd(
     const key = args[2];
     const gop = try map.getOrPut(util.gpa, key);
     if (gop.found_existing) return;
-    errdefer assert(map.remove(args[1]));
+    errdefer assert(map.remove(key));
     gop.key_ptr.* = try std.mem.dupe(util.gpa, u8, key);
 }