diff --git a/web/api/v1/api.go b/web/api/v1/api.go
index ac40c398e..df6d2e658 100644
--- a/web/api/v1/api.go
+++ b/web/api/v1/api.go
@@ -469,7 +469,7 @@ func returnAPIError(err error) *apiError {
 		return nil
 	}
 
-	switch err.(type) {
+	switch errors.Cause(err).(type) {
 	case promql.ErrQueryCanceled:
 		return &apiError{errorCanceled, err}
 	case promql.ErrQueryTimeout:
diff --git a/web/api/v1/api_test.go b/web/api/v1/api_test.go
index a70a10762..54b8b633c 100644
--- a/web/api/v1/api_test.go
+++ b/web/api/v1/api_test.go
@@ -1193,7 +1193,7 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, testLabelAPI
 				},
 			},
 			response: map[string][]metadata{
-				"go_threads": []metadata{
+				"go_threads": {
 					{textparse.MetricTypeGauge, "Number of OS threads created", ""},
 					{textparse.MetricTypeGauge, "Number of OS threads that were created.", ""},
 				},
@@ -1279,7 +1279,7 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, testLabelAPI
 				},
 			},
 			response: map[string][]metadata{
-				"go_threads": []metadata{
+				"go_threads": {
 					{textparse.MetricTypeGauge, "Number of OS threads created", ""},
 					{textparse.MetricTypeGauge, "Number of OS threads that were created.", ""},
 				},
@@ -2719,6 +2719,42 @@ func TestTSDBStatus(t *testing.T) {
 	}
 }
 
+func TestReturnAPIError(t *testing.T) {
+	cases := []struct {
+		err      error
+		expected errorType
+	}{
+		{
+			err:      promql.ErrStorage{Err: errors.New("storage error")},
+			expected: errorInternal,
+		}, {
+			err:      errors.Wrap(promql.ErrStorage{Err: errors.New("storage error")}, "wrapped"),
+			expected: errorInternal,
+		}, {
+			err:      promql.ErrQueryTimeout("timeout error"),
+			expected: errorTimeout,
+		}, {
+			err:      errors.Wrap(promql.ErrQueryTimeout("timeout error"), "wrapped"),
+			expected: errorTimeout,
+		}, {
+			err:      promql.ErrQueryCanceled("canceled error"),
+			expected: errorCanceled,
+		}, {
+			err:      errors.Wrap(promql.ErrQueryCanceled("canceled error"), "wrapped"),
+			expected: errorCanceled,
+		}, {
+			err:      errors.New("exec error"),
+			expected: errorExec,
+		},
+	}
+
+	for _, c := range cases {
+		actual := returnAPIError(c.err)
+		testutil.NotOk(t, actual)
+		testutil.Equals(t, c.expected, actual.typ)
+	}
+}
+
 // This is a global to avoid the benchmark being optimized away.
 var testResponseWriter = httptest.ResponseRecorder{}