diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d58a109..a71016a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,8 +14,8 @@ permissions:
   contents: read
 
 jobs:
-  test:
-    name: Tests
+  jvm:
+    name: JVM And Lint
     runs-on: ubuntu-latest
 
     steps:
@@ -36,3 +36,37 @@ jobs:
 
       - name: Check formatting
         run: ./gradlew :phosphor-core:ktlintCheck
+
+  ios_compile:
+    name: iOS Compile
+    runs-on: macos-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'zulu'
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Compile iOS target
+        run: ./gradlew :phosphor-core:compileKotlinIosArm64
+
+  test:
+    name: Tests
+    runs-on: ubuntu-latest
+    needs: [jvm, ios_compile]
+    if: ${{ always() }}
+
+    steps:
+      - name: Enforce required checks
+        run: |
+          if [ "${{ needs.jvm.result }}" != "success" ] || [ "${{ needs.ios_compile.result }}" != "success" ]; then
+            echo "Required CI jobs did not all pass."
+            exit 1
+          fi
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 952dbe9..f41a654 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -47,7 +47,7 @@ jobs:
         uses: gradle/actions/setup-gradle@v4
 
       - name: Run tests before publish
-        run: ./gradlew :phosphor-core:jvmTest
+        run: ./gradlew :phosphor-core:jvmTest :phosphor-core:compileKotlinIosArm64
 
       - name: Decode signing key
         if: ${{ github.event.inputs.dry_run != 'true' }}
diff --git a/phosphor-core/src/commonMain/kotlin/link/socket/phosphor/color/NeutralColor.kt b/phosphor-core/src/commonMain/kotlin/link/socket/phosphor/color/NeutralColor.kt
index d51448e..260669d 100644
--- a/phosphor-core/src/commonMain/kotlin/link/socket/phosphor/color/NeutralColor.kt
+++ b/phosphor-core/src/commonMain/kotlin/link/socket/phosphor/color/NeutralColor.kt
@@ -1,5 +1,6 @@
 package link.socket.phosphor.color
 
+import kotlin.jvm.JvmInline
 import kotlin.math.abs
 import kotlin.math.roundToInt
 
@@ -29,9 +30,9 @@ value class NeutralColor private constructor(
     val alphaInt: Int get() = (packedRgba and CHANNEL_MASK).toInt()
 
     fun toHex(includeAlpha: Boolean = true): String {
-        val rgb = "%02X%02X%02X".format(redInt, greenInt, blueInt)
+        val rgb = channelToHex(redInt) + channelToHex(greenInt) + channelToHex(blueInt)
         return if (includeAlpha) {
-            "#$rgb%02X".format(alphaInt)
+            "#$rgb${channelToHex(alphaInt)}"
         } else {
             "#$rgb"
         }
@@ -155,5 +156,7 @@ value class NeutralColor private constructor(
         ): Float = start + ((end - start) * t)
 
         private fun toChannel(value: Float): Int = (value.coerceIn(0f, 1f) * CHANNEL_MAX_FLOAT).roundToInt()
+
+        private fun channelToHex(channel: Int): String = channel.toString(radix = 16).uppercase().padStart(2, '0')
     }
 }
diff --git a/phosphor-core/src/commonTest/kotlin/link/socket/phosphor/color/NeutralColorTest.kt b/phosphor-core/src/commonTest/kotlin/link/socket/phosphor/color/NeutralColorTest.kt
index 9789d7d..4da61c6 100644
--- a/phosphor-core/src/commonTest/kotlin/link/socket/phosphor/color/NeutralColorTest.kt
+++ b/phosphor-core/src/commonTest/kotlin/link/socket/phosphor/color/NeutralColorTest.kt
@@ -76,6 +76,13 @@ class NeutralColorTest {
         assertEquals("#AABBCC", color.toHex(includeAlpha = false))
     }
 
+    @Test
+    fun `toHex pads channels with leading zeros`() {
+        val color = NeutralColor.fromHex("#010A0B0C")
+
+        assertEquals("#010A0B0C", color.toHex())
+    }
+
     @Test
     fun `fromRgba clamps out of range channels`() {
         val color = NeutralColor.fromRgba(-1f, 0.5f, 2f, 9f)