diff --git a/zoomable/src/main/java/net/engawapg/lib/zoomable/ZoomState.kt b/zoomable/src/main/java/net/engawapg/lib/zoomable/ZoomState.kt
index e72552b..603f078 100644
--- a/zoomable/src/main/java/net/engawapg/lib/zoomable/ZoomState.kt
+++ b/zoomable/src/main/java/net/engawapg/lib/zoomable/ZoomState.kt
@@ -16,6 +16,7 @@
 
 package net.engawapg.lib.zoomable
 
+import androidx.annotation.FloatRange
 import androidx.compose.animation.core.Animatable
 import androidx.compose.animation.core.DecayAnimationSpec
 import androidx.compose.animation.core.exponentialDecay
@@ -40,10 +41,14 @@ import kotlin.math.abs
  */
 @Stable
 class ZoomState(
-    private val maxScale: Float,
+    @FloatRange(from = 1.0) private val maxScale: Float = 5f,
     private var contentSize: Size = Size.Zero,
     private val velocityDecay: DecayAnimationSpec<Float> = exponentialDecay(),
 ) {
+    init {
+        require(maxScale >= 1.0f) { "maxScale must be at least 1.0." }
+    }
+
     private var _scale = Animatable(1f).apply {
         updateBounds(0.9f, maxScale)
     }
@@ -226,7 +231,7 @@ class ZoomState(
  */
 @Composable
 fun rememberZoomState(
-    maxScale: Float = 5f,
+    @FloatRange(from = 1.0) maxScale: Float = 5f,
     contentSize: Size = Size.Zero,
     velocityDecay: DecayAnimationSpec<Float> = exponentialDecay(),
 ) = remember {
diff --git a/zoomable/src/test/java/net/engawapg/lib/zoomable/ZoomStateTest.kt b/zoomable/src/test/java/net/engawapg/lib/zoomable/ZoomStateTest.kt
new file mode 100644
index 0000000..73fb84b
--- /dev/null
+++ b/zoomable/src/test/java/net/engawapg/lib/zoomable/ZoomStateTest.kt
@@ -0,0 +1,29 @@
+package net.engawapg.lib.zoomable
+
+import org.junit.Assert.*
+import org.junit.Test
+
+class ZoomStateTest {
+
+    @Test
+    fun zoomState_noArgs_instantiated() {
+        val zoomState = ZoomState()
+        assertNotNull(zoomState)
+    }
+
+    @Test
+    fun zoomState_maxScale_1_instantiated() {
+        val zoomState = ZoomState(maxScale = 1.0f)
+        assertNotNull(zoomState)
+    }
+
+    @Test
+    fun zoomState_maxScale_099_throwException() {
+        assertThrows(
+            "maxScale must be at least 1.0.",
+            IllegalArgumentException::class.java
+        ) {
+            ZoomState(maxScale = 0.99f)
+        }
+    }
+}
\ No newline at end of file