diff --git a/huma.go b/huma.go
index d0566e6b..09aea2b2 100644
--- a/huma.go
+++ b/huma.go
@@ -692,8 +692,19 @@ func Register[I, O any](api API, op Operation, handler func(context.Context, *I)
 		}
 	}
 
+	if op.RequestBody != nil {
+		for _, mediatype := range op.RequestBody.Content {
+			if mediatype.Schema != nil {
+				// Ensure all schema validation errors are set up properly as some
+				// parts of the schema may have been user-supplied.
+				mediatype.Schema.PrecomputeMessages()
+			}
+		}
+	}
+
 	var inSchema *Schema
 	if op.RequestBody != nil && op.RequestBody.Content != nil && op.RequestBody.Content["application/json"] != nil && op.RequestBody.Content["application/json"].Schema != nil {
+		hasInputBody = true
 		inSchema = op.RequestBody.Content["application/json"].Schema
 	}
 
@@ -1263,7 +1274,7 @@ func Register[I, O any](api API, op Operation, handler func(context.Context, *I)
 						}
 					}
 
-					if hasInputBody {
+					if hasInputBody && len(inputBodyIndex) > 0 {
 						// We need to get the body into the correct type now that it has been
 						// validated. Benchmarks on Go 1.20 show that using `json.Unmarshal` a
 						// second time is faster than `mapstructure.Decode` or any of the other
diff --git a/huma_test.go b/huma_test.go
index d4e5ade4..3856dad8 100644
--- a/huma_test.go
+++ b/huma_test.go
@@ -1687,7 +1687,6 @@ Content of example2.txt.
 						},
 					},
 				}
-				customSchema.PrecomputeMessages()
 
 				huma.Register(api, huma.Operation{
 					Method: http.MethodPut,
@@ -2160,6 +2159,44 @@ func TestSchemaWithExample(t *testing.T) {
 	assert.Equal(t, 1, example)
 }
 
+func TestCustomSchemaErrors(t *testing.T) {
+	// Ensure that custom schema errors are correctly reported without having
+	// to manually call `schema.PrecomputeMessages()`.
+	_, api := humatest.New(t, huma.DefaultConfig("Test API", "1.0.0"))
+
+	huma.Register(api, huma.Operation{
+		OperationID: "test",
+		Method:      http.MethodPost,
+		Path:        "/test",
+		RequestBody: &huma.RequestBody{
+			Content: map[string]*huma.MediaType{
+				"application/json": {
+					Schema: &huma.Schema{
+						Type:                 huma.TypeObject,
+						Required:             []string{"test"},
+						AdditionalProperties: false,
+						Properties: map[string]*huma.Schema{
+							"test": {
+								Type:    huma.TypeInteger,
+								Minimum: Ptr(10.0),
+							},
+						},
+					},
+				},
+			},
+		},
+	}, func(ctx context.Context, input *struct {
+		RawBody []byte
+	}) (*struct{}, error) {
+		return nil, nil
+	})
+
+	resp := api.Post("/test", map[string]any{"test": 1})
+
+	assert.Equal(t, http.StatusUnprocessableEntity, resp.Result().StatusCode)
+	assert.Contains(t, resp.Body.String(), `expected number \u003e= 10`)
+}
+
 func TestBodyRace(t *testing.T) {
 	// Run with the following:
 	// go test -run=TestBodyRace -race -parallel=100
diff --git a/schema.go b/schema.go
index 4c11a643..98d208b9 100644
--- a/schema.go
+++ b/schema.go
@@ -681,7 +681,9 @@ func schemaFromType(r Registry, t reflect.Type) *Schema {
 	v := reflect.New(t).Interface()
 	if sp, ok := v.(SchemaProvider); ok {
 		// Special case: type provides its own schema. Do not try to generate.
-		return sp.Schema(r)
+		custom := sp.Schema(r)
+		custom.PrecomputeMessages()
+		return custom
 	}
 
 	// Handle special cases.