diff --git a/lib/roo/excelx/sheet_doc.rb b/lib/roo/excelx/sheet_doc.rb
index adbb77a8..7a09725a 100755
--- a/lib/roo/excelx/sheet_doc.rb
+++ b/lib/roo/excelx/sheet_doc.rb
@@ -211,10 +211,19 @@ def extract_cells(relationships)
         extracted_cells = {}
         empty_cell = @options[:empty_cell]
 
-        doc.xpath('/worksheet/sheetData/row/c').each do |cell_xml|
-          coordinate = ::Roo::Utils.extract_coordinate(cell_xml["r"])
-          cell = cell_from_xml(cell_xml, hyperlinks(relationships)[coordinate], coordinate, empty_cell)
-          extracted_cells[coordinate] = cell if cell
+        doc.xpath('/worksheet/sheetData/row').each.with_index(1) do |row_xml, ycoord|
+          row_xml.xpath('c').each.with_index(1) do |cell_xml, xcoord|
+            r = cell_xml['r']
+            coordinate =
+              if r.nil?
+                ::Roo::Excelx::Coordinate.new(ycoord, xcoord)
+              else
+                ::Roo::Utils.extract_coordinate(r)
+              end
+
+            cell = cell_from_xml(cell_xml, hyperlinks(relationships)[coordinate], coordinate, empty_cell)
+            extracted_cells[coordinate] = cell if cell
+          end
         end
 
         expand_merged_ranges(extracted_cells) if @options[:expand_merged_ranges]
diff --git a/test/files/implicit_coordinates.xlsx b/test/files/implicit_coordinates.xlsx
new file mode 100644
index 00000000..039d0187
Binary files /dev/null and b/test/files/implicit_coordinates.xlsx differ
diff --git a/test/roo/test_excelx.rb b/test/roo/test_excelx.rb
index 61161f07..c90cd8c0 100644
--- a/test/roo/test_excelx.rb
+++ b/test/roo/test_excelx.rb
@@ -341,6 +341,15 @@ def test_parsing_xlsx_with_richtext
     assert_equal "Example richtext", xlsx.cell("b", 1)
   end
 
+  def test_implicit_coordinates
+    xlsx = roo_class.new(File.join(TESTDIR, 'implicit_coordinates.xlsx'))
+
+    assert_equal 'Test', xlsx.cell('a', 1)
+    assert_equal 'A2', xlsx.cell('a', 2)
+    assert_equal 'B2', xlsx.cell(2, 2)
+    assert_equal 'C2', xlsx.cell('c', 2)
+  end
+
   def roo_class
     Roo::Excelx
   end