diff --git a/src/sf_iov.c b/src/sf_iov.c
index 0c86667..cbbdcfb 100644
--- a/src/sf_iov.c
+++ b/src/sf_iov.c
@@ -140,11 +140,11 @@ int sf_iova_next_slice(SFDynamicIOVArray *iova,
     return iova_slice(iova, slice_len);
 }
 
-int sf_iova_memset_ex(struct iovec *iov, const int iovcnt,
+int sf_iova_memset_ex(const struct iovec *iov, const int iovcnt,
         int c, const int offset, const int length)
 {
-    struct iovec *iob;
-    struct iovec *end;
+    const struct iovec *iob;
+    const struct iovec *end;
     int sum_bytes;
     int remain_len;
     int left_bytes;
diff --git a/src/sf_iov.h b/src/sf_iov.h
index 05ee0ac..e0e6a7e 100644
--- a/src/sf_iov.h
+++ b/src/sf_iov.h
@@ -76,7 +76,7 @@ int sf_iova_first_slice(SFDynamicIOVArray *iova, const int slice_len);
 int sf_iova_next_slice(SFDynamicIOVArray *iova,
         const int consume_len, const int slice_len);
 
-int sf_iova_memset_ex(struct iovec *iov, const int iovcnt,
+int sf_iova_memset_ex(const struct iovec *iov, const int iovcnt,
         int c, const int offset, const int length);
 
 #define sf_iova_memset(iova, c, offset, length) \