diff --git a/BUILD b/BUILD
index cbc47891..cb7fbf23 100644
--- a/BUILD
+++ b/BUILD
@@ -33,3 +33,11 @@ load("@com_github_bazelbuild_buildtools//buildifier:def.bzl", "buildifier")
 buildifier(
     name = "buildifier",
 )
+
+load("@io_bazel_rules_go//go:def.bzl", "nogo")
+
+nogo(
+    name = "nogo",
+    vet = True,
+    visibility = ["//visibility:public"], # must have public visibility
+)
diff --git a/WORKSPACE b/WORKSPACE
index df0b2690..73c98286 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -119,7 +119,7 @@ go_repository(
 
 go_rules_dependencies()
 
-go_register_toolchains(go_version = "1.20.5")
+go_register_toolchains(go_version = "1.20.5", nogo = "@//:nogo")
 
 http_archive(
     name = "com_github_grpc_grpc",
diff --git a/dc/m6220-proxy/cli/cli.go b/dc/m6220-proxy/cli/cli.go
index 2e89ca8f..689a1d13 100644
--- a/dc/m6220-proxy/cli/cli.go
+++ b/dc/m6220-proxy/cli/cli.go
@@ -114,7 +114,7 @@ func (c *Client) logIn(ctx context.Context) error {
 		return fmt.Errorf("invalid username prompt: %v", err)
 	}
 	if err := c.writeLine(ctx, c.username); err != nil {
-		return fmt.Errorf("could not write username: %v")
+		return fmt.Errorf("could not write username: %v", err)
 	}
 
 	// Provide password.
@@ -126,7 +126,7 @@ func (c *Client) logIn(ctx context.Context) error {
 		return fmt.Errorf("invalid password prompt: %v", err)
 	}
 	if err := c.writeLine(ctx, c.password); err != nil {
-		return fmt.Errorf("could not write password: %v")
+		return fmt.Errorf("could not write password: %v", err)
 	}
 
 	// Get unprivileged prompt.
@@ -141,7 +141,7 @@ func (c *Client) logIn(ctx context.Context) error {
 	// Enable privileged mode.
 
 	if err := c.writeLine(ctx, "enable"); err != nil {
-		return fmt.Errorf("could not write enable: %v")
+		return fmt.Errorf("could not write enable: %v", err)
 	}
 
 	// Provide password (again)
@@ -153,7 +153,7 @@ func (c *Client) logIn(ctx context.Context) error {
 		return fmt.Errorf("invalid password prompt: %v", err)
 	}
 	if err := c.writeLine(ctx, c.password); err != nil {
-		return fmt.Errorf("could not write password: %v")
+		return fmt.Errorf("could not write password: %v", err)
 	}
 
 	// Get privileged prompt.
diff --git a/devtools/hackdoc/config/config_test.go b/devtools/hackdoc/config/config_test.go
index ba542fe9..9650d2e5 100644
--- a/devtools/hackdoc/config/config_test.go
+++ b/devtools/hackdoc/config/config_test.go
@@ -44,7 +44,7 @@ func TestParse(t *testing.T) {
 		t.Run(test.name, func(t *testing.T) {
 			got, err := parseToml([]byte(test.data))
 			if err != nil {
-				t.Fatalf("could not parse config: %w", err)
+				t.Fatalf("could not parse config: %v", err)
 			}
 			if diff := deep.Equal(test.want, got); diff != nil {
 				t.Fatal(diff)
diff --git a/go/mirko/revproxy_test.go b/go/mirko/revproxy_test.go
index d2379061..1f31cec1 100644
--- a/go/mirko/revproxy_test.go
+++ b/go/mirko/revproxy_test.go
@@ -68,7 +68,7 @@ func TestHTTPRemoteClient(t *testing.T) {
 			}
 		} else {
 			if te.wantIP != nil || te.wantPort != 0 {
-				t.Errorf("%d: wanted %v %d, got failure", te.wantIP, te.wantPort)
+				t.Errorf("%d: wanted %v %d, got failure", i, te.wantIP, te.wantPort)
 			}
 		}
 	}
diff --git a/go/pki/locate.go b/go/pki/locate.go
index 1d7e45c9..062c9344 100644
--- a/go/pki/locate.go
+++ b/go/pki/locate.go
@@ -49,7 +49,7 @@ type creds struct {
 func loadDeveloperCredentials() (*creds, error) {
 	path, err := DeveloperCredentialsLocation()
 	if err != nil {
-		return nil, fmt.Errorf("DeveloperCredentialsLocation: %w")
+		return nil, fmt.Errorf("DeveloperCredentialsLocation: %w", err)
 	}
 
 	c := creds{}
diff --git a/hswaw/site/calendar/event_test.go b/hswaw/site/calendar/event_test.go
index 1e95306a..3ebbfb0a 100644
--- a/hswaw/site/calendar/event_test.go
+++ b/hswaw/site/calendar/event_test.go
@@ -15,7 +15,7 @@ func TestWarsawDate(t *testing.T) {
 		}
 		ti, err := time.ParseInLocation("2006/01/02 15:04", s, warsaw)
 		if err != nil {
-			t.Fatal("could not parse test time %q: %v", s, err)
+			t.Fatalf("could not parse test time %q: %v", s, err)
 		}
 		return EventTime{
 			Time: ti,
@@ -25,7 +25,7 @@ func TestWarsawDate(t *testing.T) {
 		t.Helper()
 		ti, err := time.Parse("2006/01/02", s)
 		if err != nil {
-			t.Fatal("could not parse test day %q: %v", s, err)
+			t.Fatalf("could not parse test day %q: %v", s, err)
 		}
 		return EventTime{
 			Time:     ti,
diff --git a/hswaw/site/calendar/load.go b/hswaw/site/calendar/load.go
index 177ddc88..58897763 100644
--- a/hswaw/site/calendar/load.go
+++ b/hswaw/site/calendar/load.go
@@ -41,7 +41,7 @@ func (e eventBySooner) Less(i, j int) bool {
 func parseUpcomingEvents(now time.Time, data io.Reader) ([]*UpcomingEvent, error) {
 	cal, err := ics.ParseCalendar(data)
 	if err != nil {
-		return nil, fmt.Errorf("ParseCalendar(%q): %w", err)
+		return nil, fmt.Errorf("ParseCalendar(%q): %w", data, err)
 	}
 
 	var out []*UpcomingEvent