diff --git a/src/renderer/BaseRenderLayer.ts b/src/renderer/BaseRenderLayer.ts
index 1747c428..a55b090d 100644
--- a/src/renderer/BaseRenderLayer.ts
+++ b/src/renderer/BaseRenderLayer.ts
@@ -20,7 +20,7 @@ export abstract class BaseRenderLayer implements IRenderLayer {
   private _scaledCharLeft: number = 0;
   private _scaledCharTop: number = 0;
 
-  private _charAtlas: BaseCharAtlas;
+  protected _charAtlas: BaseCharAtlas;
 
   constructor(
     private _container: HTMLElement,
diff --git a/src/renderer/TextRenderLayer.ts b/src/renderer/TextRenderLayer.ts
index 2487a294..edef316b 100644
--- a/src/renderer/TextRenderLayer.ts
+++ b/src/renderer/TextRenderLayer.ts
@@ -54,6 +54,8 @@ export class TextRenderLayer extends BaseRenderLayer {
       return;
     }
 
+    this._charAtlas.beginFrame();
+
     for (let y = startRow; y <= endRow; y++) {
       const row = y + terminal.buffer.ydisp;
       const line = terminal.buffer.lines.get(row);
diff --git a/src/renderer/atlas/BaseCharAtlas.ts b/src/renderer/atlas/BaseCharAtlas.ts
index 8656f212..2680bd10 100644
--- a/src/renderer/atlas/BaseCharAtlas.ts
+++ b/src/renderer/atlas/BaseCharAtlas.ts
@@ -25,6 +25,15 @@ export default abstract class BaseCharAtlas {
    */
   protected _doWarmUp(): void { }
 
+  /**
+   * Called when we start drawing a new frame.
+   *
+   * TODO: We rely on this getting called by TextRenderLayer. This should really be called by
+   * Renderer instead, but we need to make Renderer the source-of-truth for the char atlas, instead
+   * of BaseRenderLayer.
+   */
+  public beginFrame(): void { }
+
   /**
    * May be called before warmUp finishes, however it is okay for the implementation to
    * do nothing and return false in that case.
diff --git a/src/renderer/atlas/DynamicCharAtlas.ts b/src/renderer/atlas/DynamicCharAtlas.ts
index 63da8807..7a89dac9 100644
--- a/src/renderer/atlas/DynamicCharAtlas.ts
+++ b/src/renderer/atlas/DynamicCharAtlas.ts
@@ -19,6 +19,14 @@ const TRANSPARENT_COLOR = {
   rgba: 0,
 }
 
+// Drawing to the cache is expensive: If we have to draw more than this number of glyphs to the
+// cache in a single frame, give up on trying to cache anything else, and try to finish the current
+// frame ASAP.
+//
+// This helps to limit the amount of damage a program can do when it would otherwise thrash the
+// cache.
+const DRAW_TO_CACHE_LIMIT = 100;
+
 interface IGlyphCacheValue {
   index: number;
   isEmpty: boolean;
@@ -44,6 +52,8 @@ export default class DynamicCharAtlas extends BaseCharAtlas {
   private _width: number;
   private _height: number;
 
+  private _drawToCacheCount: number = 0;
+
   constructor(document: Document, private _config: ICharAtlasConfig) {
     super();
     this._cacheCanvas = document.createElement('canvas');
@@ -69,6 +79,10 @@ export default class DynamicCharAtlas extends BaseCharAtlas {
     // document.body.appendChild(this._cacheCanvas);
   }
 
+  public beginFrame(): void {
+    this._drawToCacheCount = 0;
+  }
+
   public draw(
     ctx: CanvasRenderingContext2D,
     glyph: IGlyphIdentifier,
@@ -80,7 +94,7 @@ export default class DynamicCharAtlas extends BaseCharAtlas {
     if (cacheValue != null) {
       this._drawFromCache(ctx, cacheValue, x, y);
       return true;
-    } else if (this._canCache(glyph)) {
+    } else if (this._canCache(glyph) && this._drawToCacheCount < DRAW_TO_CACHE_LIMIT) {
       let index;
       if (this._cacheMap.size < this._cacheMap.capacity) {
         index = this._cacheMap.size;
@@ -142,6 +156,7 @@ export default class DynamicCharAtlas extends BaseCharAtlas {
   // TODO: We do this (or something similar) in multiple places. We should split this off
   // into a shared function.
   private _drawToCache(glyph: IGlyphIdentifier, index: number): IGlyphCacheValue {
+    this._drawToCacheCount++;
 
     // draw the background
     let backgroundColor;