diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java
index 1bbd03b..d557063 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java
@@ -24,7 +24,11 @@
  * C++-related file type definitions.
  */
 public final class CppFileTypes {
-  public static final FileType CPP_SOURCE = FileType.of(".cc", ".cpp", ".cxx", ".c++", ".C");
+  // .cu and .cl are CUDA and OpenCL source extensions, respectively. They are expected to only be
+  // supported with clang. Bazel is not officially supporting these targets, and the extensions are
+  // listed only as long as they work with the existing C++ actions.
+  public static final FileType CPP_SOURCE =
+      FileType.of(".cc", ".cpp", ".cxx", ".c++", ".C", ".cu", ".cl");
   public static final FileType C_SOURCE = FileType.of(".c");
   public static final FileType OBJC_SOURCE = FileType.of(".m");
   public static final FileType OBJCPP_SOURCE = FileType.of(".mm");
diff --git a/tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator/Constants.java b/tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator/Constants.java
index 2961382..a4b1b53 100644
--- a/tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator/Constants.java
+++ b/tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator/Constants.java
@@ -53,6 +53,6 @@
   // Please keep in sync with the extensions in CppFileTypes.
   static final ImmutableList<String> CC_EXTENSIONS =
       ImmutableList.of(
-          ".cc", ".cpp", ".cxx", ".c++", ".C", ".c", ".h", ".hh", ".hpp", ".ipp", ".hxx", ".inc",
-          ".inl", ".tlh", ".tli", ".H");
+          ".cc", ".cpp", ".cxx", ".c++", ".C", ".c", ".cu", ".cl", ".h", ".hh", ".hpp", ".ipp",
+          ".hxx", ".inc", ".inl", ".tlh", ".tli", ".H");
 }