diff --git a/src/History.js b/src/History.js
index ae0be54..2b5c70e 100644
--- a/src/History.js
+++ b/src/History.js
@@ -130,7 +130,7 @@ export default class History extends Component {
 				let newState = {
 					progressHistoryIncomplete: this.state.progressHistoryIncomplete,
 				};
-				delete newState.progressHistoryIncomplete[progressIndex];
+				newState.progressHistoryIncomplete.splice(progressIndex, 1);
 				this.setState(newState);
 			});
 	}
diff --git a/src/LoggedInHome.js b/src/LoggedInHome.js
index 33f358f..09d5d24 100644
--- a/src/LoggedInHome.js
+++ b/src/LoggedInHome.js
@@ -226,7 +226,7 @@ export default withRouter(class LoggedInHome extends React.Component {
 				let newState = {
 					progressHistoryIncomplete: this.state.progressHistoryIncomplete,
 				};
-				delete newState.progressHistoryIncomplete[progressIndex];
+				newState.progressHistoryIncomplete.splice(progressIndex, 1);
 				this.setState(newState);
 			});
 	}