diff --git a/src/csharp/ext/grpc_csharp_ext.c b/src/csharp/ext/grpc_csharp_ext.c
index 9a1c908d11b..e182468d9b0 100644
--- a/src/csharp/ext/grpc_csharp_ext.c
+++ b/src/csharp/ext/grpc_csharp_ext.c
@@ -731,7 +731,7 @@ grpcsharp_ssl_credentials_create(const char *pem_root_certs,
   }
 }
 
-GPR_EXPORT void grpcsharp_credentials_release(grpc_credentials *creds) {
+GPR_EXPORT void GPR_CALLTYPE grpcsharp_credentials_release(grpc_credentials *creds) {
   grpc_credentials_release(creds);
 }
 
@@ -765,7 +765,7 @@ grpcsharp_ssl_server_credentials_create(
   return creds;
 }
 
-GPR_EXPORT void grpcsharp_server_credentials_release(
+GPR_EXPORT void GPR_CALLTYPE grpcsharp_server_credentials_release(
     grpc_server_credentials *creds) {
   grpc_server_credentials_release(creds);
 }