diff --git a/CHANGES b/CHANGES
index 8095e279..93450571 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,6 @@
 XXXX-XX-XX
 
+* The Data Matrix encoder was fixed to always emit the Macro 05/06 codeword in the first position.
 * The performance of the QR Code encoder was improved for data that mixes character classes, such as mixed-case text and URLs, by materialising each mode segment once when the mode changes rather than extending it character by character.
 
 
diff --git a/src/datamatrix.ps.src b/src/datamatrix.ps.src
index 6f6e1224..f2487005 100644
--- a/src/datamatrix.ps.src
+++ b/src/datamatrix.ps.src
@@ -976,6 +976,13 @@ begin
             % Compensate c40headerlength if any
             c40headerlength 0 gt { /c40headerlength c40headerlength 1 add def } if
         } if
+        % Macro 05/06 is only recognised when its codeword is first
+        msg 0 get //datamatrix.m05 eq msg 0 get //datamatrix.m06 eq or {
+            Avals msg 0 get get addtocws
+            /i 1 def
+            % Compensate c40headerlength if any
+            c40headerlength 0 gt { /c40headerlength c40headerlength 1 add def } if
+        } if
         {
             i msglen ge {exit} if
             //datamatrix.encfuncs mode get load exec
diff --git a/tests/ps_tests/datamatrix.ps.test b/tests/ps_tests/datamatrix.ps.test
index 5c0bb84e..f200d18b 100644
--- a/tests/ps_tests/datamatrix.ps.test
+++ b/tests/ps_tests/datamatrix.ps.test
@@ -68,7 +68,7 @@
 } def
 
 
-% Macro 05
+% Macro 05/06
 
 {
     ([\)>^03005^029214^030^004) (debugcws parse) datamatrix  % Short 05
@@ -78,6 +78,14 @@
     ([\)>^03005^02921456^030^004) (debugcws parse) datamatrix  % 05 with 6 in processed position 5
 } [236 151 175 55 129] debugIsEqual
 
+{
+    ([\)>^03005^029AAAAAAA^030^004) (debugcws parse) datamatrix  % 05 macro codeword must be first, so it precedes a C40 latch
+} [236 230 89 191 89 191 254 66] debugIsEqual
+
+{
+    ([\)>^03006^029tttttttt^030^004) (debugcws parse) datamatrix  % 06 ahead of a Text latch
+} [237 239 211 138 211 138 211 105] debugIsEqual
+
 
 % Metrics loops