diff --git a/README.md b/README.md
index 7dfbdc0..52c09ae 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ See below sections for what this package currently contains.
 
 ## Clang Thread Safety Annotation Macros
 
-The `rcpputils/thread_safety_annotations.h` header provides macros for Clang's [Thread Safety Analysis](https://clang.llvm.org/docs/ThreadSafetyAnalysis.html) feature.
+The `rcpputils/thread_safety_annotations.hpp` header provides macros for Clang's [Thread Safety Analysis](https://clang.llvm.org/docs/ThreadSafetyAnalysis.html) feature.
 
 The macros allow you to annotate your code, but expand to nothing when using a non-clang compiler, so they are safe for cross-platform use.
 
diff --git a/include/rcpputils/thread_safety_annotations.h b/include/rcpputils/thread_safety_annotations.hpp
similarity index 96%
rename from include/rcpputils/thread_safety_annotations.h
rename to include/rcpputils/thread_safety_annotations.hpp
index adb8caf..1c8b2d8 100644
--- a/include/rcpputils/thread_safety_annotations.h
+++ b/include/rcpputils/thread_safety_annotations.hpp
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef RCPPUTILS__THREAD_SAFETY_ANNOTATIONS_H_
-#define RCPPUTILS__THREAD_SAFETY_ANNOTATIONS_H_
+#ifndef RCPPUTILS__THREAD_SAFETY_ANNOTATIONS_HPP_
+#define RCPPUTILS__THREAD_SAFETY_ANNOTATIONS_HPP_
 
 #include <mutex>
 
@@ -97,4 +97,4 @@ inline const std::mutex & operator!(const std::mutex & a)
 #define RCPPUTILS_TSA_NO_THREAD_SAFETY_ANALYSIS \
   RCPPUTILS_THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
 
-#endif  // RCPPUTILS__THREAD_SAFETY_ANNOTATIONS_H_
+#endif  // RCPPUTILS__THREAD_SAFETY_ANNOTATIONS_HPP_
diff --git a/test/test_basic.cpp b/test/test_basic.cpp
index 121864f..6d0d726 100644
--- a/test/test_basic.cpp
+++ b/test/test_basic.cpp
@@ -14,7 +14,7 @@
 
 #include "gtest/gtest.h"
 
-#include "rcpputils/thread_safety_annotations.h"
+#include "rcpputils/thread_safety_annotations.hpp"
 
 /*
 Macros tested