diff --git a/R/pkg-sf.R b/R/pkg-sf.R
index 5c3bb3a6..3a7c04b0 100644
--- a/R/pkg-sf.R
+++ b/R/pkg-sf.R
@@ -138,7 +138,7 @@ wk_crs_proj_definition.crs <- function(crs, proj_version = NULL, verbose = FALSE
 #' @export
 wk_crs_projjson.crs <- function(crs) {
   json <- crs$ProjJson
-  if (is.null(json)) {
+  if (is.null(json) || is.na(json[1])) {
     # i.e., GDAL is not >= 3.1.0
     NextMethod()
   } else {