diff --git a/docutils/parsers/rst/tableparser.py b/docutils/parsers/rst/tableparser.py
index 2cd3879..fd24424 100644
--- a/docutils/parsers/rst/tableparser.py
+++ b/docutils/parsers/rst/tableparser.py
@@ -511,8 +511,8 @@ class SimpleTableParser(TableParser):
                 if i == lastcol and line[end:].strip():
                     text = line[start:].rstrip()
                     new_end = start + len(text)
-                    columns[i] = (start, new_end)
                     main_start, main_end = self.columns[-1]
+                    columns[i] = (start, max(main_end, new_end))
                     if new_end > main_end:
                         self.columns[-1] = (main_start, new_end)
                 elif line[end:nextstart].strip():
diff --git a/test/test_parsers/test_rst/test_tables.py b/test/test_parsers/test_rst/test_tables.py
index ed7e177..28b8070 100755
--- a/test/test_parsers/test_rst/test_tables.py
+++ b/test/test_parsers/test_rst/test_tables.py
@@ -789,6 +789,56 @@ A table with three  columns.
 """],
 ["""\
 ==============  ======
+A simple table  this text extends to the right
+cell 3          as does this text
+==============  ======
+""",
+"""\
+<document source="test data">
+    <table>
+        <tgroup cols="2">
+            <colspec colwidth="14">
+            <colspec colwidth="30">
+            <tbody>
+                <row>
+                    <entry>
+                        <paragraph>
+                            A simple table
+                    <entry>
+                        <paragraph>
+                            this text extends to the right
+                <row>
+                    <entry>
+                        <paragraph>
+                            cell 3
+                    <entry>
+                        <paragraph>
+                            as does this text
+"""],
+["""\
+==============  ======
+A simple table  this text extends to the right
+                continuation of cell 2
+==============  ======
+""",
+"""\
+<document source="test data">
+    <table>
+        <tgroup cols="2">
+            <colspec colwidth="14">
+            <colspec colwidth="30">
+            <tbody>
+                <row>
+                    <entry>
+                        <paragraph>
+                            A simple table
+                    <entry>
+                        <paragraph>
+                            this text extends to the right
+                            continuation of cell 2
+"""],
+["""\
+==============  ======
 A simple table  with
 no bottom       border
 """,