diff --git a/src/format.c b/src/format.c
index 906fd62..92a9c93 100644
--- a/src/format.c
+++ b/src/format.c
@@ -7,9 +7,16 @@
 
 #include "format.h"
 
-#define WRITE(w, buf, len) w.write(w.opaque, buf, len)
 #define TRY FMT_TRY
 
+static bool
+write(struct apfl_format_writer w, const char *buf, size_t len)
+{
+    return len == 0
+        ? true
+        : w.write(w.opaque, buf, len);
+}
+
 static bool
 write_file(void *opaque, const char *buf, size_t len)
 {
@@ -45,7 +52,7 @@ apfl_format_string_writer(struct apfl_string_builder *sb)
 bool
 apfl_format_put_string_view(struct apfl_format_writer w, struct apfl_string_view sv)
 {
-    return WRITE(w, sv.bytes, sv.len);
+    return write(w, sv.bytes, sv.len);
 }
 
 #define PUT_INT_BUFSIZE 21 // ceil(log10(2**64)) + 1
@@ -56,13 +63,13 @@ apfl_format_put_int(struct apfl_format_writer w, int i)
     char buf[PUT_INT_BUFSIZE];
     size_t len = snprintf(buf, PUT_INT_BUFSIZE, "%d", i);
     assert(len < PUT_INT_BUFSIZE);
-    return WRITE(w, buf, len);
+    return write(w, buf, len);
 }
 
 bool
 apfl_format_put_char(struct apfl_format_writer w, char c)
 {
-    return WRITE(w, &c, 1);
+    return write(w, &c, 1);
 }
 
 #define PUT_HEXBYTE_BUFSIZE 3
@@ -73,7 +80,7 @@ apfl_format_put_hexbyte(struct apfl_format_writer w, unsigned char c)
     char buf[PUT_HEXBYTE_BUFSIZE];
     size_t len = snprintf(buf, PUT_HEXBYTE_BUFSIZE, "%x", (unsigned) c);
     assert(len < PUT_HEXBYTE_BUFSIZE);
-    return WRITE(w, buf, len);
+    return write(w, buf, len);
 }
 
 bool
@@ -101,7 +108,7 @@ apfl_format_put_number(struct apfl_format_writer w, apfl_number number)
 {
     char buf[PUT_NUMBER_BUFSIZE];
     size_t len = snprintf(buf, PUT_NUMBER_BUFSIZE, "%f", number);
-    TRY(WRITE(w, buf, len));
+    TRY(write(w, buf, len));
     if (len >= PUT_NUMBER_BUFSIZE) {
         TRY(apfl_format_put_string(w, "[...]"));
     }