diff --git a/ts/copy.bzl b/ts/copy.bzl
index 2b5302671..525814259 100644
--- a/ts/copy.bzl
+++ b/ts/copy.bzl
@@ -27,22 +27,27 @@ def copy_files(ctx, files):
 
     return [DefaultInfo(files = depset(outputs))]
 
-def copy_select_files(ctx, files, include, exclude, unwanted_prefix):
+def remove_prefix(text, prefix):
+    if text.startswith(prefix):
+        return text[len(prefix):]
+    return text
+
+def copy_select_files(ctx, files, include, exclude, base, unwanted_prefix):
     wanted = []
     for f in files.to_list():
-        path = f.path
+        path = remove_prefix(f.path, base)
         want = True
 
         for substr in exclude:
-            if substr in path:
+            if path.startswith(substr):
                 want = False
                 continue
         if not want:
             continue
 
         for substr in include:
-            if substr in path:
-                output = path.replace(unwanted_prefix, "")
+            if path.startswith(substr):
+                output = remove_prefix(path, unwanted_prefix)
                 wanted.append((f, output))
 
     return copy_files(ctx, wanted)
diff --git a/ts/css-browser-selector.bzl b/ts/css-browser-selector.bzl
index d03ee3315..db235118d 100644
--- a/ts/css-browser-selector.bzl
+++ b/ts/css-browser-selector.bzl
@@ -6,7 +6,8 @@ _include = [
     "css_browser_selector.min.js",
 ]
 
-_unwanted_prefix = "external/npm/node_modules/css-browser-selector/"
+_base = "external/npm/node_modules/css-browser-selector/"
+_unwanted_prefix = ""
 
 def _copy_css_browser_selector_impl(ctx):
     return copy_select_files(
@@ -14,6 +15,7 @@ def _copy_css_browser_selector_impl(ctx):
         ctx.attr.css_browser_selector.files,
         _include,
         [],
+        _base,
         _unwanted_prefix,
     )
 
diff --git a/ts/jquery-ui.bzl b/ts/jquery-ui.bzl
index 482aa6985..baf547270 100644
--- a/ts/jquery-ui.bzl
+++ b/ts/jquery-ui.bzl
@@ -6,7 +6,8 @@ _include = [
     "jquery-ui.min.js",
 ]
 
-_unwanted_prefix = "external/npm/node_modules/jquery-ui-dist/"
+_base = "external/npm/node_modules/jquery-ui-dist/"
+_unwanted_prefix = ""
 
 def _copy_jquery_ui_impl(ctx):
     return copy_select_files(
@@ -14,6 +15,7 @@ def _copy_jquery_ui_impl(ctx):
         ctx.attr.jquery_ui.files,
         _include,
         [],
+        _base,
         _unwanted_prefix,
     )
 
diff --git a/ts/jquery.bzl b/ts/jquery.bzl
index f7a3542d8..b7f1c4a84 100644
--- a/ts/jquery.bzl
+++ b/ts/jquery.bzl
@@ -6,7 +6,8 @@ _include = [
     "dist/jquery.min.js"
 ]
 
-_unwanted_prefix = "external/npm/node_modules/jquery/dist/"
+_base = "external/npm/node_modules/jquery/"
+_unwanted_prefix = "dist/"
 
 def _copy_jquery_impl(ctx):
     return copy_select_files(
@@ -14,6 +15,7 @@ def _copy_jquery_impl(ctx):
         ctx.attr.jquery.files,
         _include,
         [],
+        _base,
         _unwanted_prefix,
     )
 
diff --git a/ts/mathjax.bzl b/ts/mathjax.bzl
index fcfd8d517..480e1f6e3 100644
--- a/ts/mathjax.bzl
+++ b/ts/mathjax.bzl
@@ -14,7 +14,8 @@ _exclude = [
     "es5/sre/mathmaps/mathmaps_ie.js",
 ]
 
-_unwanted_prefix = "external/npm/node_modules/mathjax/es5/"
+_base = "external/npm/node_modules/mathjax/"
+_unwanted_prefix = "es5/"
 
 def _copy_mathjax_impl(ctx):
     return copy_select_files(
@@ -22,6 +23,7 @@ def _copy_mathjax_impl(ctx):
         ctx.attr.mathjax.files,
         _include,
         _exclude,
+        _base,
         _unwanted_prefix,
     )
 
diff --git a/ts/protobufjs.bzl b/ts/protobufjs.bzl
index 80a26f26c..25c947251 100644
--- a/ts/protobufjs.bzl
+++ b/ts/protobufjs.bzl
@@ -6,7 +6,8 @@ _include = [
     "dist/protobuf.min.js",
 ]
 
-_unwanted_prefix = "external/npm/node_modules/protobufjs/dist/"
+_base = "external/npm/node_modules/protobufjs/"
+_unwanted_prefix = "dist/"
 
 def _copy_protobufjs_impl(ctx):
     return copy_select_files(
@@ -14,6 +15,7 @@ def _copy_protobufjs_impl(ctx):
         ctx.attr.protobufjs.files,
         _include,
         [],
+        _base,
         _unwanted_prefix,
     )