diff --git a/mongoose.c b/mongoose.c
index 120abbf6..9f31d735 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -986,7 +986,7 @@ static void *ff_open(const char *path, int flags) {
   if (flags & MG_FS_WRITE) mode |= FA_WRITE | FA_OPEN_ALWAYS | FA_OPEN_APPEND;
   if (f_open(&f, path, mode) == 0) {
     FIL *fp = calloc(1, sizeof(*fp));
-    *fp = f;
+    memcpy(fp, &f, sizeof(*fp));
     return fp;
   } else {
     return NULL;
diff --git a/src/fs_fat.c b/src/fs_fat.c
index 7c2846fe..2997dd67 100644
--- a/src/fs_fat.c
+++ b/src/fs_fat.c
@@ -74,7 +74,7 @@ static void *ff_open(const char *path, int flags) {
   if (flags & MG_FS_WRITE) mode |= FA_WRITE | FA_OPEN_ALWAYS | FA_OPEN_APPEND;
   if (f_open(&f, path, mode) == 0) {
     FIL *fp = calloc(1, sizeof(*fp));
-    *fp = f;
+    memcpy(fp, &f, sizeof(*fp));
     return fp;
   } else {
     return NULL;