diff --git a/internal/config/trusted_proxies_internal_test.go b/internal/config/trusted_proxies_internal_test.go
new file mode 100644
index 0000000..b2593c0
--- /dev/null
+++ b/internal/config/trusted_proxies_internal_test.go
@@ -0,0 +1,65 @@
+package config
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestTrustedProxiesConfig checks the trusted_proxies key wiring: a valid
+// CIDR list lands in TrustedProxies in order, and an omitted key trusts no
+// one. The list parser itself is shared with blocked_networks and is
+// exercised in depth by that key's tests.
+func TestTrustedProxiesConfig(t *testing.T) {
+	t.Parallel()
+
+	t.Run("valid list is parsed in order", func(t *testing.T) {
+		t.Parallel()
+
+		c, err := configFromYAML(t,
+			signingKeyLine+`trusted_proxies: ["10.0.0.0/8", "2001:db8::/32"]`+"\n")
+		if err != nil {
+			t.Fatalf("valid trusted_proxies should load: %v", err)
+		}
+
+		got := make([]string, len(c.TrustedProxies))
+		for i, p := range c.TrustedProxies {
+			got[i] = p.String()
+		}
+
+		if joined := strings.Join(got, ","); joined != "10.0.0.0/8,2001:db8::/32" {
+			t.Errorf("TrustedProxies = %v, want the two ranges in order", got)
+		}
+	})
+
+	t.Run("omitted key trusts no one", func(t *testing.T) {
+		t.Parallel()
+
+		c, err := configFromYAML(t, signingKeyLine)
+		if err != nil {
+			t.Fatalf("minimal config should load: %v", err)
+		}
+
+		if len(c.TrustedProxies) != 0 {
+			t.Errorf("TrustedProxies = %v, want empty", c.TrustedProxies)
+		}
+	})
+}
+
+// TestTrustedProxiesInvalidAbortsStartup checks that an invalid or null
+// value aborts startup with an error naming the key and the offending value.
+func TestTrustedProxiesInvalidAbortsStartup(t *testing.T) {
+	t.Parallel()
+
+	runAbortCases(t, []abortCase{
+		{
+			name:              "invalid cidr",
+			yaml:              signingKeyLine + `trusted_proxies: ["999.0.0.0/8"]` + "\n",
+			wantErrSubstrings: []string{keyTrustedProxies, "999.0.0.0/8"},
+		},
+		{
+			name:              "null value",
+			yaml:              signingKeyLine + "trusted_proxies:\n",
+			wantErrSubstrings: []string{keyTrustedProxies, nullValueText},
+		},
+	})
+}