diff --git a/src/utils/sha1.h b/src/utils/sha1.h
index 2dac3ea2..a40d7fa1 100644
--- a/src/utils/sha1.h
+++ b/src/utils/sha1.h
@@ -57,7 +57,7 @@ private:
         ConvertOp convertOp) -> auto {
         char digest[DigestSize];
 
-        auto ret = digestOp(reinterpret_cast<const unsigned char *>(input.c_str()),
+        const auto ret = (*digestOp)(reinterpret_cast<const unsigned char *>(input.c_str()),
                  input.size(), reinterpret_cast<unsigned char *>(digest));
         assert(ret == 0);