diff --git a/test/posix-test.cc b/test/posix-test.cc
index d4f0ddf3..e3061240 100644
--- a/test/posix-test.cc
+++ b/test/posix-test.cc
@@ -175,7 +175,7 @@ int test::fclose(FILE *stream) {
   return ::fclose(stream);
 }
 
-int test::fileno(FILE *stream) {
+int (test::fileno)(FILE *stream) {
   EMULATE_EINTR(fileno, -1);
   return ::FMT_POSIX(fileno(stream));
 }
diff --git a/test/posix-test.h b/test/posix-test.h
index 17bf0c97..7afbbbe8 100644
--- a/test/posix-test.h
+++ b/test/posix-test.h
@@ -72,8 +72,7 @@ int pipe(int *pfds, unsigned psize, int textmode);
 
 FILE *fopen(const char *filename, const char *mode);
 int fclose(FILE *stream);
-int fileno(FILE *stream);
-
+int (fileno)(FILE *stream);
 }  // namespace test
 
 #define FMT_SYSTEM(call) test::call