diff --git a/internal/shop.cm b/internal/shop.cm
index c8545949..1143f3c1 100644
--- a/internal/shop.cm
+++ b/internal/shop.cm
@@ -13,14 +13,33 @@ var os = use('internal/os')
 var link = use('link')
 
 // These come from env (via core_extras in engine.cm):
-//   analyze, run_ast_fn, core_json, use_cache, shop_path, actor_api, runtime_env,
-//   content_hash, cache_path, ensure_build_dir
+//   analyze, run_ast_fn, core_json, use_cache, core_path, shop_path, actor_api,
+//   runtime_env, content_hash, cache_path, ensure_build_dir
 var shop_json = core_json
 var global_shop_path = shop_path
 var my$_ = actor_api
 
 var core = "core"
 
+// Compiler fingerprint: hash of all compiler source files so that any compiler
+// change invalidates the entire build cache. Folded into hash_path().
+var compiler_fingerprint = (function() {
+  var files = [
+    "tokenize", "parse", "fold", "mcode", "streamline",
+    "qbe", "qbe_emit", "ir_stats"
+  ]
+  var combined = ""
+  var i = 0
+  var path = null
+  while (i < length(files)) {
+    path = core_path + '/' + files[i] + '.cm'
+    if (fd.is_file(path))
+      combined = combined + text(fd.slurp(path))
+    i = i + 1
+  }
+  return content_hash(stone(blob(combined)))
+})()
+
 // Make a package name safe for use in C identifiers.
 // Replaces /, ., -, @ with _ so the result is a valid C identifier fragment.
 function safe_c_name(name) {
@@ -43,7 +62,7 @@ function put_into_cache(content, obj)
 function hash_path(content, salt)
 {
   var s = salt || 'mach'
-  return global_shop_path + '/build/' + content_hash(stone(blob(text(content) + '\n' + s)))
+  return global_shop_path + '/build/' + content_hash(stone(blob(text(content) + '\n' + s + '\n' + compiler_fingerprint)))
 }
 
 var Shop = {}