diff --git a/src/output.ts b/src/output.ts
index 0df8fbe..cee1ff2 100644
--- a/src/output.ts
+++ b/src/output.ts
@@ -35,7 +35,11 @@ export function formatOutput(data: unknown, format: OutputFormat): string {
 function formatTable(data: unknown): string {
   if (Array.isArray(data)) {
     if (data.length === 0) return "(empty)"
-    const keys = Object.keys(data[0] as Record<string, unknown>)
+    const keys = [
+      ...new Set(
+        data.flatMap(row => Object.keys(row as Record<string, unknown>)),
+      ),
+    ]
     const widths = keys.map(key =>
       Math.max(
         key.length,
diff --git a/test/output.test.ts b/test/output.test.ts
index 4a4af80..b414d5c 100644
--- a/test/output.test.ts
+++ b/test/output.test.ts
@@ -38,6 +38,22 @@ describe("formatOutput", () => {
       expect(formatOutput([], "table")).toBe("(empty)")
     })
 
+    it("includes fields that first appear on later array rows", () => {
+      const data = [
+        { name: "CryptoPunk #1", price: "10 ETH" },
+        { name: "Bored Ape #2", price: "5 ETH", rarity: "Rare" },
+      ]
+      const result = formatOutput(data, "table")
+      const lines = result.split("\n")
+
+      expect(lines[0]).toContain("name")
+      expect(lines[0]).toContain("price")
+      expect(lines[0]).toContain("rarity")
+      expect(lines[2]).toContain("CryptoPunk #1")
+      expect(lines[3]).toContain("Bored Ape #2")
+      expect(lines[3]).toContain("Rare")
+    })
+
     it("returns (empty) for empty object", () => {
       expect(formatOutput({}, "table")).toBe("(empty)")
     })