diff --git a/.gitignore b/.gitignore
index 2865b2ec..12144cd2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,3 +38,13 @@ nosetests.xml
 # custom
 indexer_tests
 
+# These folders in cpp/llvm contain lots of upstream cruft we don't care
+# about and would rather not have in our tree...
+docs/*
+examples/*
+www/*
+
+# ... but excluding these LLVMBuild.txt files breaks the build so we need to
+# explicitely include them
+!LLVMBuild.txt
+
diff --git a/cpp/llvm/.gitignore b/cpp/llvm/.gitignore
index 425473af..4d68b0e8 100644
--- a/cpp/llvm/.gitignore
+++ b/cpp/llvm/.gitignore
@@ -36,6 +36,9 @@ projects/*
 !projects/sample
 !projects/CMakeLists.txt
 !projects/Makefile
+
+# The build breakes without this file
+!projects/LLVMBuild.txt
 # Clang, which is tracked independently.
 # tools/clang
 # LLDB, which is tracked independently.