diff --git a/apps/boot/ChangeLog b/apps/boot/ChangeLog
index e3f492d3b..a43ecf86e 100644
--- a/apps/boot/ChangeLog
+++ b/apps/boot/ChangeLog
@@ -51,3 +51,4 @@
 0.45: Fix 0.44 regression (auto-add semi-colon between each boot code chunk)
 0.46: Fix no clock found error on Bangle.js 2
 0.47: Add polyfill for setUI with an object as an argument (fix regression for 2v12 devices after Layout module changed)
+0.48: Workaround for BTHRM issues on Bangle.js 1 (write .boot files in chunks)
diff --git a/apps/boot/bootupdate.js b/apps/boot/bootupdate.js
index 119cd2c2c..4cb3c52e4 100644
--- a/apps/boot/bootupdate.js
+++ b/apps/boot/bootupdate.js
@@ -197,8 +197,18 @@ bootFiles.forEach(bootFile=>{
   require('Storage').write('.boot0',"//"+bootFile+"\n",fileOffset);
   fileOffset+=2+bootFile.length+1;
   var bf = require('Storage').read(bootFile);
-  require('Storage').write('.boot0',bf,fileOffset);
-  fileOffset+=bf.length;
+  // we can't just write 'bf' in one go because at least in 2v13 and earlier
+  // Espruino wants to read the whole file into RAM first, and on Bangle.js 1
+  // it can be too big (especially BTHRM).
+  var bflen = bf.length;
+  var bfoffset = 0;
+  while (bflen) {
+    var bfchunk = Math.min(bflen, 2048);
+    require('Storage').write('.boot0',bf.substr(bfoffset, bfchunk),fileOffset);
+    fileOffset+=bfchunk;
+    bfoffset+=bfchunk;
+    bflen-=bfchunk;
+  }
   require('Storage').write('.boot0',";\n",fileOffset);
   fileOffset+=2;
 });
diff --git a/apps/boot/metadata.json b/apps/boot/metadata.json
index d1bf2edde..62adc4db1 100644
--- a/apps/boot/metadata.json
+++ b/apps/boot/metadata.json
@@ -1,7 +1,7 @@
 {
   "id": "boot",
   "name": "Bootloader",
-  "version": "0.47",
+  "version": "0.48",
   "description": "This is needed by Bangle.js to automatically load the clock, menu, widgets and settings",
   "icon": "bootloader.png",
   "type": "bootloader",