diff --git a/src/TerminalLine.ts b/src/TerminalLine.ts
index 7f944191..186e2f58 100644
--- a/src/TerminalLine.ts
+++ b/src/TerminalLine.ts
@@ -95,7 +95,7 @@ export class TerminalLine {
       this.push(fill);
     }
   }
-  
+
   /** replace cells from pos to pos + n - 1 with fill */
   public replaceCells(start: number, end: number, fill: CharData): void {
     while (start < end  && start < this.length) this.set(start++, fill);  // Note: fill is not cloned
diff --git a/src/renderer/CharacterJoinerRegistry.test.ts b/src/renderer/CharacterJoinerRegistry.test.ts
index d427ef5e..d7cd1ce4 100644
--- a/src/renderer/CharacterJoinerRegistry.test.ts
+++ b/src/renderer/CharacterJoinerRegistry.test.ts
@@ -260,16 +260,13 @@ describe('CharacterJoinerRegistry', () => {
   });
 });
 
-interface IPartialLineData {
-  [0]: string;
-  [1]?: number;
-}
+type IPartialLineData = ([string] | [string, number]);
 
 function lineData(data: IPartialLineData[]): TerminalLine {
   const tline = new TerminalLine();
   for (let i = 0; i < data.length; ++i) {
     const line = data[i][0];
-    const attr = data[i][1] || 0;
+    const attr = <number>(data[i][1] || 0);
     line.split('').map(char => tline.push([attr, char, 1, char.charCodeAt(0)]));
   }
   return tline;