diff --git a/R/ISOAbstractObject.R b/R/ISOAbstractObject.R
index 30d4a7de..3a8e55fb 100644
--- a/R/ISOAbstractObject.R
+++ b/R/ISOAbstractObject.R
@@ -918,7 +918,7 @@ ISOAbstractObject <- R6Class("ISOAbstractObject",
           }
         }
       }))
-      
+      nsdefs <- nsdefs[!duplicated(names(nsdefs))]
       return(nsdefs)
     },
     
diff --git a/tests/testthat/test_GMLRectifiedGrid.R b/tests/testthat/test_GMLRectifiedGrid.R
index 072a5530..df1144bd 100644
--- a/tests/testthat/test_GMLRectifiedGrid.R
+++ b/tests/testthat/test_GMLRectifiedGrid.R
@@ -12,8 +12,10 @@ context("GMLRectifiedGrid")
 test_that("GMLRectifiedGrid",{
   #encoding
   md <- GMLRectifiedGrid$new()
-  md$setGridEnvelope(0, 500, 0, 500)
-  md$setAxisLabels("E", "N")
+  m <- matrix(c(-180,180,-90, 90), nrow = 2, ncol = 2, byrow = TRUE,
+              dimnames = list(c("x", "y"), c("min","max")))
+  md$setGridEnvelope(m = m)
+  md$setAxisLabels(c("E", "N"))
   md$setOrigin(15,15)
   md$addOffsetVector(c(0,15))
   xml <- md$encode()
diff --git a/tests/testthat/test_GMLReferenceableGrid.R b/tests/testthat/test_GMLReferenceableGrid.R
index 7ea7fe8d..aad61fa1 100644
--- a/tests/testthat/test_GMLReferenceableGrid.R
+++ b/tests/testthat/test_GMLReferenceableGrid.R
@@ -12,8 +12,8 @@ context("GMLReferenceableGrid")
 test_that("GMLAbstractReferenceableGrid",{
   #encoding
   md <- GMLAbstractReferenceableGrid$new()
-  envelope <- matrix(c(0,500,0,500),2,2)
-  md$setGridEnvelope(envelope)
+  m <- matrix(c(0,500,0,500),2,2)
+  md$setGridEnvelope(m = m)
   md$setAxisLabels(c("E", "N"))
   xml <- md$encode(validate = FALSE)
   expect_is(xml, "XMLInternalNode")