diff --git a/format.h b/format.h
index 52e8d5b3..1f217b5e 100644
--- a/format.h
+++ b/format.h
@@ -25,6 +25,8 @@
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #ifndef FMT_FORMAT_H_
 #define FMT_FORMAT_H_
 
diff --git a/posix.h b/posix.h
index a2cf2b13..8ae38bec 100644
--- a/posix.h
+++ b/posix.h
@@ -25,6 +25,8 @@
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #ifndef FMT_POSIX_H_
 #define FMT_POSIX_H_
 
diff --git a/test/gtest-extra.h b/test/gtest-extra.h
index df9cb7f0..d34e8188 100644
--- a/test/gtest-extra.h
+++ b/test/gtest-extra.h
@@ -25,6 +25,8 @@
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #ifndef FMT_GTEST_EXTRA_H_
 #define FMT_GTEST_EXTRA_H_
 
diff --git a/test/mock-allocator.h b/test/mock-allocator.h
index 7de1e1a0..8b23aaf6 100644
--- a/test/mock-allocator.h
+++ b/test/mock-allocator.h
@@ -25,6 +25,8 @@
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #ifndef FMT_MOCK_ALLOCATOR_H_
 #define FMT_MOCK_ALLOCATOR_H_
 
diff --git a/test/posix-test.h b/test/posix-test.h
index 4768cb94..60242439 100644
--- a/test/posix-test.h
+++ b/test/posix-test.h
@@ -25,6 +25,8 @@
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #ifndef FMT_POSIX_TEST_H
 #define FMT_POSIX_TEST_H