diff --git a/iwyu.cc b/iwyu.cc
index 3e4afd2..2c2a138 100644
--- a/iwyu.cc
+++ b/iwyu.cc
@@ -109,15 +109,15 @@
 #include "iwyu_location_util.h"
 #include "iwyu_output.h"
 #include "iwyu_path_util.h"
-#include "iwyu_use_flags.h"
+#include "iwyu_port.h"  // for CHECK_
 // This is needed for
 // preprocessor_info().PublicHeaderIntendsToProvide().  Somehow IWYU
 // removes it mistakenly.
 #include "iwyu_preprocessor.h"  // IWYU pragma: keep
 #include "iwyu_stl_util.h"
 #include "iwyu_string_util.h"
+#include "iwyu_use_flags.h"
 #include "iwyu_verrs.h"
-#include "port.h"  // for CHECK_
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/raw_ostream.h"
 #include "clang/AST/ASTConsumer.h"
diff --git a/iwyu_ast_util.cc b/iwyu_ast_util.cc
index 261fb38..9453394 100644
--- a/iwyu_ast_util.cc
+++ b/iwyu_ast_util.cc
@@ -18,10 +18,10 @@
 #include "iwyu_globals.h"
 #include "iwyu_location_util.h"
 #include "iwyu_path_util.h"
+#include "iwyu_port.h"  // for CHECK_
 #include "iwyu_stl_util.h"
 #include "iwyu_string_util.h"
 #include "iwyu_verrs.h"
-#include "port.h"  // for CHECK_
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/raw_ostream.h"
diff --git a/iwyu_ast_util.h b/iwyu_ast_util.h
index eac49ca..f62437b 100644
--- a/iwyu_ast_util.h
+++ b/iwyu_ast_util.h
@@ -16,8 +16,8 @@
 #include <set>                          // for set
 #include <string>                       // for string
 
+#include "iwyu_port.h"  // for CHECK_
 #include "iwyu_use_flags.h"
-#include "port.h"  // for CHECK_
 #include "llvm/Support/Casting.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/NestedNameSpecifier.h"
diff --git a/iwyu_cache.h b/iwyu_cache.h
index 4d696c2..2efe2f3 100644
--- a/iwyu_cache.h
+++ b/iwyu_cache.h
@@ -19,8 +19,8 @@
 #include <set>                          // for set
 #include <utility>                      // for pair
 
+#include "iwyu_port.h"  // for CHECK_
 #include "iwyu_stl_util.h"
-#include "port.h"  // for CHECK_
 
 namespace clang {
 class NamedDecl;
diff --git a/iwyu_globals.cc b/iwyu_globals.cc
index 7070a18..0f58b4d 100644
--- a/iwyu_globals.cc
+++ b/iwyu_globals.cc
@@ -23,11 +23,11 @@
 #include "iwyu_lexer_utils.h"
 #include "iwyu_location_util.h"
 #include "iwyu_path_util.h"
+#include "iwyu_port.h"  // for CHECK_, etc
 #include "iwyu_stl_util.h"
 #include "iwyu_string_util.h"
 #include "iwyu_verrs.h"
 #include "iwyu_version.h"
-#include "port.h"  // for CHECK_, etc
 #include "llvm/Support/raw_ostream.h"
 #include "clang/AST/PrettyPrinter.h"
 #include "clang/Basic/FileManager.h"
diff --git a/iwyu_include_picker.cc b/iwyu_include_picker.cc
index 710e46d..2bdf578 100644
--- a/iwyu_include_picker.cc
+++ b/iwyu_include_picker.cc
@@ -23,10 +23,10 @@
 
 #include "iwyu_location_util.h"
 #include "iwyu_path_util.h"
+#include "iwyu_port.h"
 #include "iwyu_stl_util.h"
 #include "iwyu_string_util.h"
 #include "iwyu_verrs.h"
-#include "port.h"  // for CHECK_
 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Casting.h"
diff --git a/iwyu_lexer_utils.cc b/iwyu_lexer_utils.cc
index 0475600..fcea2d2 100644
--- a/iwyu_lexer_utils.cc
+++ b/iwyu_lexer_utils.cc
@@ -9,10 +9,10 @@
 
 #include "iwyu_lexer_utils.h"
 #include "iwyu_globals.h"
+#include "iwyu_port.h"  // for CHECK_
 
 #include <string>
 
-#include "port.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Token.h"
diff --git a/iwyu_output.h b/iwyu_output.h
index 719f821..60da058 100644
--- a/iwyu_output.h
+++ b/iwyu_output.h
@@ -21,9 +21,9 @@
 #include <string>                       // for string, operator<
 #include <vector>                       // for vector
 
+#include "iwyu_port.h"  // for CHECK_
 #include "iwyu_stl_util.h"
 #include "iwyu_use_flags.h"
-#include "port.h"  // for CHECK_
 #include "clang/AST/Decl.h"
 #include "clang/Basic/SourceLocation.h"
 
diff --git a/port.h b/iwyu_port.h
similarity index 100%
rename from port.h
rename to iwyu_port.h
diff --git a/iwyu_preprocessor.cc b/iwyu_preprocessor.cc
index 4640631..58e7859 100644
--- a/iwyu_preprocessor.cc
+++ b/iwyu_preprocessor.cc
@@ -23,10 +23,10 @@
 #include "iwyu_location_util.h"
 #include "iwyu_output.h"
 #include "iwyu_path_util.h"
+#include "iwyu_port.h"  // for CHECK_
 #include "iwyu_stl_util.h"
 #include "iwyu_string_util.h"
 #include "iwyu_verrs.h"
-#include "port.h"  // for CHECK_
 // TODO(wan): remove this once the IWYU bug is fixed.
 // IWYU pragma: no_include "foo/bar/baz.h"
 #include "llvm/Support/raw_ostream.h"
diff --git a/iwyu_preprocessor.h b/iwyu_preprocessor.h
index 2f060e7..3f0bbf4 100644
--- a/iwyu_preprocessor.h
+++ b/iwyu_preprocessor.h
@@ -66,7 +66,7 @@
 #include <vector>                       // for vector
 
 #include "iwyu_output.h"
-#include "port.h"
+#include "iwyu_port.h"  // for CHECK_
 
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManager.h"
diff --git a/iwyu_string_util.h b/iwyu_string_util.h
index f1b1e5e..78c2dc7 100644
--- a/iwyu_string_util.h
+++ b/iwyu_string_util.h
@@ -18,7 +18,7 @@
 #include <string>
 #include <vector>
 
-#include "port.h"
+#include "iwyu_port.h"
 
 namespace include_what_you_use {