diff --git a/mongoose.c b/mongoose.c
index ec0b1acd..fe8ff5b2 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -1533,10 +1533,13 @@ int mg_iobuf_init(struct mg_iobuf *io, size_t size) {
 
 size_t mg_iobuf_append(struct mg_iobuf *io, const void *buf, size_t len,
                        size_t chunk_size) {
-  size_t new_size = io->len + len + chunk_size;
-  new_size -= new_size % chunk_size;
-  if (new_size != io->size) mg_iobuf_resize(io, new_size);
-  if (new_size != io->size) len = 0;  // Realloc failure, append nothing
+  size_t new_size = io->len + len;
+  if (new_size > io->size) {
+    new_size += chunk_size;
+    new_size -= new_size % chunk_size;
+    if (new_size != io->size) mg_iobuf_resize(io, new_size);
+    if (new_size != io->size) len = 0;  // Realloc failure, append nothing
+  }
   if (buf != NULL) memmove(io->buf + io->len, buf, len);
   io->len += len;
   return len;
diff --git a/mongoose.h b/mongoose.h
index 4fe646a1..5da8b471 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -127,7 +127,16 @@
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stdint.h>
+
+#if defined(__GNUC__)
 #include <sys/time.h>
+#else
+typedef long suseconds_t;
+struct timeval {
+  time_t tv_sec;
+  suseconds_t tv_usec;
+};
+#endif
 
 #if MG_ENABLE_FS
 #include <sys/stat.h>
diff --git a/src/iobuf.c b/src/iobuf.c
index 0d0826a3..3275f20b 100644
--- a/src/iobuf.c
+++ b/src/iobuf.c
@@ -44,10 +44,13 @@ int mg_iobuf_init(struct mg_iobuf *io, size_t size) {
 
 size_t mg_iobuf_append(struct mg_iobuf *io, const void *buf, size_t len,
                        size_t chunk_size) {
-  size_t new_size = io->len + len + chunk_size;
-  new_size -= new_size % chunk_size;
-  if (new_size != io->size) mg_iobuf_resize(io, new_size);
-  if (new_size != io->size) len = 0;  // Realloc failure, append nothing
+  size_t new_size = io->len + len;
+  if (new_size > io->size) {
+    new_size += chunk_size;
+    new_size -= new_size % chunk_size;
+    if (new_size != io->size) mg_iobuf_resize(io, new_size);
+    if (new_size != io->size) len = 0;  // Realloc failure, append nothing
+  }
   if (buf != NULL) memmove(io->buf + io->len, buf, len);
   io->len += len;
   return len;