diff --git a/pygmt/src/blockm.py b/pygmt/src/blockm.py
index 22f6cbd43c5..f175cbf3de1 100644
--- a/pygmt/src/blockm.py
+++ b/pygmt/src/blockm.py
@@ -77,7 +77,7 @@ def _blockm(block_method, table, outfile, x, y, z, **kwargs):
     s="skiprows",
     w="wrap",
 )
-@kwargs_to_strings(R="sequence")
+@kwargs_to_strings(R="sequence", i="sequence_comma")
 def blockmean(table=None, outfile=None, *, x=None, y=None, z=None, **kwargs):
     r"""
     Block average (x,y,z) data tables by mean estimation.
@@ -148,7 +148,7 @@ def blockmean(table=None, outfile=None, *, x=None, y=None, z=None, **kwargs):
     s="skiprows",
     w="wrap",
 )
-@kwargs_to_strings(R="sequence")
+@kwargs_to_strings(R="sequence", i="sequence_comma")
 def blockmedian(table=None, outfile=None, *, x=None, y=None, z=None, **kwargs):
     r"""
     Block average (x,y,z) data tables by median estimation.
diff --git a/pygmt/src/grdtrack.py b/pygmt/src/grdtrack.py
index 4756fad5a33..b3ebdd8c3ae 100644
--- a/pygmt/src/grdtrack.py
+++ b/pygmt/src/grdtrack.py
@@ -31,7 +31,7 @@
     j="distcalc",
     n="interpolation",
 )
-@kwargs_to_strings(R="sequence", S="sequence")
+@kwargs_to_strings(R="sequence", S="sequence", i="sequence_comma")
 def grdtrack(points, grid, newcolname=None, outfile=None, **kwargs):
     r"""
     Sample grids at specified (x,y) locations.
diff --git a/pygmt/src/text.py b/pygmt/src/text.py
index 1b1d4007700..e8b042f4537 100644
--- a/pygmt/src/text.py
+++ b/pygmt/src/text.py
@@ -46,6 +46,7 @@
     font="sequence_comma",
     justify="sequence_comma",
     c="sequence_comma",
+    i="sequence_comma",
     p="sequence",
 )
 def text_(