diff --git a/R/find_rev.R b/R/find_rev.R
index 10bdd428..434095fc 100644
--- a/R/find_rev.R
+++ b/R/find_rev.R
@@ -390,8 +390,8 @@ USE_RSTUDIO};
 
 
 #' Invoke shell command `nix-build` from an R session
-#' @param nix_file File path to the `default.nix` file. The default is
-#' a `default.nix` file in the current working directory of the current R
+#' @param project_path Path to the folder where the `default.nix` file resides. 
+#  The default is `".`, which is the current working directory in the R session.
 #' session.
 #' @param exec_mode Either `"blocking"` (default) or `"non-blocking`. This
 #' will either block the R session while the `nix-build` shell command is
@@ -400,9 +400,11 @@ USE_RSTUDIO};
 #' launched, if `nix_build()` call is assigned to an R object. Otherwise, it 
 #' will be returned as "invisible".
 #' @export
-nix_build <- function(nix_file = file.path("default.nix"),
+nix_build <- function(project_path = ".",
                       exec_mode = c("blocking", "non-blocking")) {
   has_nix_build <- nix_build_installed() # TRUE if yes, FALSE if no
+  nix_file <- file.path(project_path, "default.nix")
+  
   stopifnot(
     "Argument `nix_file` must be character of length 1." =
       is.character(nix_file) && length(nix_file) == 1L,
@@ -441,7 +443,7 @@ nix_build <- function(nix_file = file.path("default.nix"),
     }
   }
   
-  # clean zombies for background/non-blocking mode
+  # todo (?): clean zombies for background/non-blocking mode
   # rm(pid)
   
   return(invisible(proc))
diff --git a/dev/build_envs.Rmd b/dev/build_envs.Rmd
index 157a2bb8..cd807ca5 100644
--- a/dev/build_envs.Rmd
+++ b/dev/build_envs.Rmd
@@ -476,8 +476,8 @@ session.
 
 ```{r function-nix_build}
 #' Invoke shell command `nix-build` from an R session
-#' @param nix_file File path to the `default.nix` file. The default is
-#' a `default.nix` file in the current working directory of the current R
+#' @param project_path Path to the folder where the `default.nix` file resides. 
+#  The default is `".`, which is the current working directory in the R session.
 #' session.
 #' @param exec_mode Either `"blocking"` (default) or `"non-blocking`. This
 #' will either block the R session while the `nix-build` shell command is
@@ -486,9 +486,11 @@ session.
 #' launched, if `nix_build()` call is assigned to an R object. Otherwise, it 
 #' will be returned as "invisible".
 #' @export
-nix_build <- function(nix_file = file.path("default.nix"),
+nix_build <- function(project_path = ".",
                       exec_mode = c("blocking", "non-blocking")) {
   has_nix_build <- nix_build_installed() # TRUE if yes, FALSE if no
+  nix_file <- file.path(project_path, "default.nix")
+  
   stopifnot(
     "Argument `nix_file` must be character of length 1." =
       is.character(nix_file) && length(nix_file) == 1L,
@@ -527,7 +529,7 @@ nix_build <- function(nix_file = file.path("default.nix"),
     }
   }
   
-  # clean zombies for background/non-blocking mode
+  # todo (?): clean zombies for background/non-blocking mode
   # rm(pid)
   
   return(invisible(proc))
diff --git a/man/nix_build.Rd b/man/nix_build.Rd
index 315dfa7a..a39a4ecd 100644
--- a/man/nix_build.Rd
+++ b/man/nix_build.Rd
@@ -4,14 +4,10 @@
 \alias{nix_build}
 \title{Invoke shell command \code{nix-build} from an R session}
 \usage{
-nix_build(
-  nix_file = file.path("default.nix"),
-  exec_mode = c("blocking", "non-blocking")
-)
+nix_build(project_path = ".", exec_mode = c("blocking", "non-blocking"))
 }
 \arguments{
-\item{nix_file}{File path to the \code{default.nix} file. The default is
-a \code{default.nix} file in the current working directory of the current R
+\item{project_path}{Path to the folder where the \code{default.nix} file resides.
 session.}
 
 \item{exec_mode}{Either \code{"blocking"} (default) or \verb{"non-blocking}. This