--- a/internal/npm_install/node_module_library.bzl
+++ b/internal/npm_install/node_module_library.bzl
@@ -29,14 +29,20 @@ def _node_module_library_impl(ctx):
     # use in rules such as ts_devserver
     scripts = depset(ctx.files.scripts)
 
-    # declarations are a subset of sources that are decleration files
-    declarations = depset([f for f in ctx.files.srcs if f.path.endswith(".d.ts")])
+    # declarations are a subset of sources that are declaration files
+
+    declarations = depset([
+        f
+        for f in ctx.files.srcs
+        if f.path.endswith(".d.ts") and
+           # exclude eg. external/npm/node_modules/protobufjs/node_modules/@types/node/index.d.ts
+           # these would be duplicates of the typings provided directly in another dependency
+           len(f.path.split("/node_modules/")) < 3
+    ])
+
+    # transitive_declarations are all .d.ts files in srcs plus those in direct & transitive dependencies
+    transitive_declarations = depset(transitive = [declarations])
 
-    # transitive_declarations are all direct & transitive decleration files
-    transitive_declarations = depset()
-    for src in ctx.attr.srcs:
-        if hasattr(src, "typescript"):
-            transitive_declarations = depset(transitive = [transitive_declarations, src.typescript.transitive_declarations])
     for dep in ctx.attr.deps:
         if hasattr(dep, "typescript"):
             transitive_declarations = depset(transitive = [transitive_declarations, dep.typescript.transitive_declarations])