diff --git a/src/style_manager/model/PropertySlider.js b/src/style_manager/model/PropertySlider.js
deleted file mode 100644
index 439b0406a..000000000
--- a/src/style_manager/model/PropertySlider.js
+++ /dev/null
@@ -1,10 +0,0 @@
-import Property from './PropertyNumber';
-
-export default class PropertySlider extends Property {
-  defaults() {
-    return {
-      ...Property.getDefaults(),
-      showInput: 1,
-    };
-  }
-}
diff --git a/src/style_manager/model/PropertySlider.ts b/src/style_manager/model/PropertySlider.ts
new file mode 100644
index 000000000..f5acf9f4b
--- /dev/null
+++ b/src/style_manager/model/PropertySlider.ts
@@ -0,0 +1,10 @@
+import PropertyNumber from './PropertyNumber';
+
+export default class PropertySlider extends PropertyNumber {
+  defaults() {
+    return {
+      ...PropertyNumber.getDefaults(),
+      showInput: 1,
+    };
+  }
+}