diff --git a/pythoncapi_compat.h b/pythoncapi_compat.h
index ecc445e..791d511 100644
--- a/pythoncapi_compat.h
+++ b/pythoncapi_compat.h
@@ -2529,6 +2529,10 @@ PyBytesWriter_WriteBytes(PyBytesWriter *writer,
     return 0;
 }
 
+static inline int
+PyBytesWriter_Format(PyBytesWriter *writer, const char *format, ...)
+                     Py_GCC_ATTRIBUTE((format(printf, 2, 0)));
+
 static inline int
 PyBytesWriter_Format(PyBytesWriter *writer, const char *format, ...)
 {
diff --git a/tests/setup.py b/tests/setup.py
index 825241e..33a0e66 100755
--- a/tests/setup.py
+++ b/tests/setup.py
@@ -34,7 +34,11 @@
         '-Wconversion',
         # /usr/lib64/pypy3.7/include/pyport.h:68:20: error: redefinition of typedef
         # 'Py_hash_t' is a C11 feature
-        "-Wno-typedef-redefinition",
+        '-Wno-typedef-redefinition',
+        # Formatting checks
+        '-Wformat',
+        '-Wformat-nonliteral',
+        '-Wformat-security',
     ))
     CFLAGS = COMMON_FLAGS + [
         # Use C99 for pythoncapi_compat.c which initializes PyModuleDef with a