diff --git a/src/bits.c b/src/bits.c
index b00293c..865e373 100644
--- a/src/bits.c
+++ b/src/bits.c
@@ -12,7 +12,8 @@
 
 static inline int sfread(void* out, size_t *restrict size, FILE* f)
 {
-	return !!(*size = (size_t)fread(out, 1, *size, f));
+	register ssize_t r = fread(out, 1, *size, f);
+	return r < 0 ? 0 : !!((*size) = (size_t)r);
 }
 
 static int fwrite_all(const void* _buf, size_t sz, size_t num, FILE* out)