diff --git a/pkg/accessreview/drivers/name_resolver.go b/pkg/accessreview/drivers/name_resolver.go
index 4a02c3420..37730bd2f 100644
--- a/pkg/accessreview/drivers/name_resolver.go
+++ b/pkg/accessreview/drivers/name_resolver.go
@@ -708,7 +708,8 @@ func (r *sentryNameResolver) ResolveInstanceName(ctx context.Context) (string, e
 		return "", nil
 	}
 
-	endpoint, err := url.JoinPath("https://sentry.io", "api", "0", "organizations", url.PathEscape(r.orgSlug))
+	// Trailing slash required; see SentryDriver.ListAccounts.
+	endpoint, err := url.JoinPath("https://sentry.io", "api", "0", "organizations", url.PathEscape(r.orgSlug)+"/")
 	if err != nil {
 		return "", fmt.Errorf("cannot build sentry organization URL: %w", err)
 	}
diff --git a/pkg/accessreview/drivers/name_resolver_test.go b/pkg/accessreview/drivers/name_resolver_test.go
index 0e2aa7d43..71c83b18a 100644
--- a/pkg/accessreview/drivers/name_resolver_test.go
+++ b/pkg/accessreview/drivers/name_resolver_test.go
@@ -170,7 +170,7 @@ func TestSentryNameResolver(t *testing.T) {
 
 			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				assert.Equal(t, http.MethodGet, r.Method)
-				assert.Equal(t, "/api/0/organizations/acme", r.URL.Path)
+				assert.Equal(t, "/api/0/organizations/acme/", r.URL.Path)
 				w.Header().Set("Content-Type", "application/json")
 				w.WriteHeader(tc.status)
 				_, _ = w.Write([]byte(tc.body))
diff --git a/pkg/accessreview/drivers/sentry.go b/pkg/accessreview/drivers/sentry.go
index f45391112..d6a95ac1d 100644
--- a/pkg/accessreview/drivers/sentry.go
+++ b/pkg/accessreview/drivers/sentry.go
@@ -101,7 +101,10 @@ func (d *SentryDriver) ListAccounts(ctx context.Context) ([]AccountRecord, error
 
 	var records []AccountRecord
 
-	nextURL, err := url.JoinPath("https://sentry.io", "api", "0", "organizations", url.PathEscape(orgSlug), "members")
+	// The trailing slash is required: Sentry's API only routes slashed
+	// paths and answers 404 (without redirecting) otherwise. url.JoinPath
+	// keeps it only when the last element carries it.
+	nextURL, err := url.JoinPath("https://sentry.io", "api", "0", "organizations", url.PathEscape(orgSlug), "members/")
 	if err != nil {
 		return nil, fmt.Errorf("cannot build sentry members URL: %w", err)
 	}
diff --git a/pkg/accessreview/drivers/sentry_test.go b/pkg/accessreview/drivers/sentry_test.go
index 23ee89029..181005a8d 100644
--- a/pkg/accessreview/drivers/sentry_test.go
+++ b/pkg/accessreview/drivers/sentry_test.go
@@ -25,6 +25,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -54,12 +55,48 @@ func TestSentryDriver(t *testing.T) {
 	assert.NotEmpty(t, r.Roles)
 }
 
+// TestSentryDriverRequestsTrailingSlashPaths pins the exact request paths
+// against Sentry's real routing: its API is Django-based and only matches
+// paths ending in a slash, answering 404 (no redirect) otherwise. A 404 is
+// indistinguishable from a revoked membership here, so dropping the slash
+// silently turns every campaign fetch into a bogus "reconnect" error.
+func TestSentryDriverRequestsTrailingSlashPaths(t *testing.T) {
+	t.Parallel()
+
+	var gotPaths []string
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotPaths = append(gotPaths, r.URL.Path)
+
+		// Mimic Sentry: unslashed paths do not route.
+		if !strings.HasSuffix(r.URL.Path, "/") {
+			w.WriteHeader(http.StatusNotFound)
+			_, _ = w.Write([]byte(`{"detail":"The requested resource does not exist"}`))
+
+			return
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`[{"id":"42","email":"alice@example.com","name":"Alice","orgRole":"member"}]`))
+	}))
+	defer srv.Close()
+
+	client := &http.Client{Transport: &hostRewriter{target: srv.URL}}
+
+	records, err := NewSentryDriver(client, "acme-corp").ListAccounts(context.Background())
+	require.NoError(t, err)
+	require.Len(t, records, 1)
+	assert.Equal(t, "alice@example.com", records[0].Email)
+	assert.Equal(t, []string{"/api/0/organizations/acme-corp/members/"}, gotPaths)
+}
+
 func TestSentryDriverListAccountsStaleSlug(t *testing.T) {
 	t.Parallel()
 
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		assert.Equal(t, http.MethodGet, r.Method)
-		assert.Equal(t, "/api/0/organizations/acme-old/members", r.URL.Path)
+		assert.Equal(t, "/api/0/organizations/acme-old/members/", r.URL.Path)
 		w.WriteHeader(http.StatusNotFound)
 		_, _ = w.Write([]byte(`{"detail":"The requested resource does not exist"}`))
 	}))
@@ -88,7 +125,7 @@ func TestSentryDriverListAccountsAutoDiscoversSlug(t *testing.T) {
 			assert.Equal(t, "true", r.URL.Query().Get("member"))
 			w.WriteHeader(http.StatusOK)
 			_, _ = w.Write([]byte(`[{"slug":"` + discoveredSlug + `","name":"Discovered Org"}]`))
-		case "/api/0/organizations/" + discoveredSlug + "/members":
+		case "/api/0/organizations/" + discoveredSlug + "/members/":
 			w.WriteHeader(http.StatusOK)
 			_, _ = w.Write([]byte(`[{"id":"42","email":"alice@example.com","name":"Alice","orgRole":"member"}]`))
 		default:
diff --git a/pkg/accessreview/drivers/testdata/sentry.yaml b/pkg/accessreview/drivers/testdata/sentry.yaml
index 599b457b3..3e0e6e9eb 100644
--- a/pkg/accessreview/drivers/testdata/sentry.yaml
+++ b/pkg/accessreview/drivers/testdata/sentry.yaml
@@ -8,7 +8,7 @@ interactions:
         proto_minor: 1
         content_length: 0
         host: sentry.io
-        url: https://sentry.io/api/0/organizations/acme-corp/members
+        url: https://sentry.io/api/0/organizations/acme-corp/members/
         method: GET
       response:
         proto: HTTP/2.0