diff --git a/R/gUtils.R b/R/gUtils.R
index 4fef890..c2472e6 100644
--- a/R/gUtils.R
+++ b/R/gUtils.R
@@ -1031,23 +1031,20 @@ gr.string = function(gr, add.chr = FALSE, mb = FALSE, round = 3, other.cols = c(
 
     str = ifelse(as.logical(strand(gr)!='*'), as.character(strand(gr)), '')
 
-    
+    ## XT debug: the lastest GRanges requires an extra ":" in between end and strand
     if (mb){
-        return(paste(sn, ':', round(start(gr)/1e6, round), '-', round(end(gr)/1e6, round), str, other.str, sep = ''))
+        return(paste(sn, ':', round(start(gr)/1e6, round), '-', round(end(gr)/1e6, round), ":", str, other.str, sep = ''))
     }
     else{
         if (pretty){
-            return(paste(sn, ':', stringr::str_trim(format(start(gr), big.mark = ',')), '-', stringr::str_trim(format(end(gr), big.mark = ',')), str, other.str, sep = ''))
+            return(paste(sn, ':', stringr::str_trim(format(start(gr), big.mark = ',')), '-', stringr::str_trim(format(end(gr), big.mark = ',')), ":", str, other.str, sep = ''))
         }
         else{
-            return(paste(sn, ':', start(gr), '-', end(gr), str, other.str, sep = ''))
+            return(paste(sn, ':', start(gr), '-', end(gr), ":", str, other.str, sep = ''))
         }
     }
 }
 
-
-
-
 #' @name grl.reduce
 #' @title grl.reduce
 #' @description
@@ -2386,6 +2383,10 @@ seg2gr = function(segs, seqlengths = NULL, seqinfo = Seqinfo())
         segs$pos1 = as.numeric(segs$pos1)
         segs$pos2 = as.numeric(segs$pos2)
 
+        ## only convert valid ranges
+        valid.ix = which(!is.na(segs$pos1) & !is.na(segs$pos2))
+        segs = segs[valid.ix, , drop=FALSE]
+        
         out = GRanges(seqnames = segs$chr, ranges = IRanges(segs$pos1, segs$pos2),strand = segs$strand, seqlengths = seqlengths)
 
     } else{
diff --git a/tests/testthat/test_rangeops.R b/tests/testthat/test_rangeops.R
index 4f5ca02..9ad70d2 100644
--- a/tests/testthat/test_rangeops.R
+++ b/tests/testthat/test_rangeops.R
@@ -351,15 +351,15 @@ test_that("gr.string", {
     expect_that(grepl("(+|-)", gr.string(example_genes)[1]), is_true())
     ## check 'if (length(gr)==0){'
     ## add.chr
-    expect_equal(gr.string(example_genes, add.chr=TRUE)[1], 'chr1:69090-70008+')
+    expect_equal(gr.string(example_genes, add.chr=TRUE)[1], 'chr1:69090-70008:+')
     ## mb
-    expect_equal(gr.string(example_genes[1], mb = TRUE), '1:0.069-0.07+')
+    expect_equal(gr.string(example_genes[1], mb = TRUE), '1:0.069-0.07:+')
     ## round
-    expect_equal(gr.string(example_genes[1], round = 1, mb=TRUE), '1:0.1-0.1+')
+    expect_equal(gr.string(example_genes[1], round = 1, mb=TRUE), '1:0.1-0.1:+')
     ## other.cols
-    expect_equal(gr.string(example_genes[1], other.cols='name'), '1:69090-70008+  OR4F5')
+    expect_equal(gr.string(example_genes[1], other.cols='name'), '1:69090-70008:+  OR4F5')
     ## pretty
-    expect_equal(gr.string(example_genes, pretty=TRUE)[1], '1:69,090-70,008+')
+    expect_equal(gr.string(example_genes, pretty=TRUE)[1], '1:69,090-70,008:+')
 
 })
 
@@ -387,12 +387,12 @@ test_that("grl.string", {
     expect_that(nchar(names(grl.string(grl.hiC[1:5])[1])) > 0, is_true())
     expect_that(grepl(",", grl.string(grl.hiC[1:5])[1]), is_true())
     ## check 'if (class(grl) == "GRanges"){'
-    expect_equal(grl.string(example_genes[1]), '1:69090-70008+')
+    expect_equal(grl.string(example_genes[1]), '1:69090-70008:+')
     ## check 'error handling'
     expect_error(grl.string('foo')) ##  Error: Input must be GRangesList (or GRanges, which is sent to gr.string)
     ## check 'else{ nm = 1:length(grl) ! 1138 }'
     names(grl1) = NULL
-    expect_equal(as.character(grl.string(grl1[2])), '9:140100229-140100229-,19:24309057-24309057-')
+    expect_equal(as.character(grl.string(grl1[2])), '9:140100229-140100229:-,19:24309057-24309057:-')
 
 })