diff --git a/dsl/http.go b/dsl/http.go
index e99cf08cf7..fe26072d87 100644
--- a/dsl/http.go
+++ b/dsl/http.go
@@ -755,7 +755,7 @@ func MapParams(args ...any) {
 	if len(args) > 0 {
 		mapName, ok = args[0].(string)
 		if !ok {
-			eval.ReportError("argument must be a string")
+			eval.InvalidArgError("string", args[0])
 		}
 	}
 	e.MapQueryParams = &mapName
diff --git a/eval/eval_test.go b/eval/eval_test.go
index bfda376449..d32d503aee 100644
--- a/eval/eval_test.go
+++ b/eval/eval_test.go
@@ -20,6 +20,7 @@ func TestInvalidArgError(t *testing.T) {
 		"ErrorName (int)":      {func() { Type("name", func() { ErrorName(1, 2) }) }, "cannot use 2 (type int) as type name"},
 		"Example":              {func() { Example(1, 2) }, "cannot use 1 (type int) as type summary (string)"},
 		"Headers":              {func() { Headers(1) }, "cannot use 1 (type int) as type function"},
+		"MapParams":            {func() { Service("s", func() { Method("m", func() { HTTP(func() { MapParams(1) }) }) }) }, "cannot use 1 (type int) as type string"},
 		"OneOf (function)":     {func() { Type("name", func() { OneOf("name", "description", 1) }) }, "cannot use 1 (type int) as type function"},
 		"OneOf (string)":       {func() { Type("name", func() { OneOf("name", 1, func() {}) }) }, "cannot use 1 (type int) as type string"},
 		"Param":                {func() { API("name", func() { HTTP(func() { Params(1) }) }) }, "cannot use 1 (type int) as type function"},