diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -7857,12 +7857,12 @@
       unpoison_file(stream);
 }
 
-INTERCEPTOR(void, setbuffer, __sanitizer_FILE *stream, char *buf, int mode) {
+INTERCEPTOR(void, setbuffer, __sanitizer_FILE *stream, char *buf, SIZE_T size) {
   void *ctx;
-  COMMON_INTERCEPTOR_ENTER(ctx, setbuffer, stream, buf, mode);
-  REAL(setbuffer)(stream, buf, mode);
+  COMMON_INTERCEPTOR_ENTER(ctx, setbuffer, stream, buf, size);
+  REAL(setbuffer)(stream, buf, size);
   if (buf) {
-    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, __sanitizer_bufsiz);
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, size);
   }
   if (stream)
     unpoison_file(stream);
diff --git a/compiler-rt/test/sanitizer_common/TestCases/Posix/setvbuf.cpp b/compiler-rt/test/sanitizer_common/TestCases/Posix/setvbuf.cpp
--- a/compiler-rt/test/sanitizer_common/TestCases/Posix/setvbuf.cpp
+++ b/compiler-rt/test/sanitizer_common/TestCases/Posix/setvbuf.cpp
@@ -34,7 +34,9 @@
 
   print_something();
 
-  setbuffer(stdout, buf, BUFSIZ);
+  // Ensure that interceptor reads correct size
+  // (not BUFSIZ as by default, hence BUFSIZ/2).
+  setbuffer(stdout, buf, BUFSIZ / 2);
 
   print_something();