diff --git a/common/engine/keyboardprocessor/tests/unit/kmx/041 - long context and deadkeys.kmn b/common/engine/keyboardprocessor/tests/unit/kmx/041 - long context and deadkeys.kmn
index dac5333238..c899b7063c 100644
--- a/common/engine/keyboardprocessor/tests/unit/kmx/041 - long context and deadkeys.kmn	
+++ b/common/engine/keyboardprocessor/tests/unit/kmx/041 - long context and deadkeys.kmn	
@@ -12,12 +12,14 @@ group(Main) using keys
 c Test 1 
 dk(1) 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh' + '1' > context '1'
 
-c Test 2
+c Test 2: Test that we haven't split a deadkey code: UC_SENTINEL CODE_DEADKEY <deadkey_number>
+c         because: CODE_DEADKEY = U+0008; deadkey_number = U+0001
 U+0008 U+0001 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh1' + '2' > 'FAIL TEST 2'
 U+0001 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh1' + '2' > 'FAIL TEST 2'
 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh1' + '2' > context '2'
 
-c Test 3
+c Test 3: Test that we haven't split a deadkey code: UC_SENTINEL CODE_DEADKEY <deadkey_number>
+c         because: CODE_DEADKEY = U+0008; deadkey_number = U+0001
 U+0008 U+0001 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh12' + '3' > 'FAIL TEST 3'
 U+0001 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh12' + '3' > 'FAIL TEST 3'
 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh12' + '3' > context '3'
diff --git a/common/engine/keyboardprocessor/tests/unit/kmx/042 - long context and split deadkeys.kmn b/common/engine/keyboardprocessor/tests/unit/kmx/042 - long context and split deadkeys.kmn
index 57a170f4de..8f840146d2 100644
--- a/common/engine/keyboardprocessor/tests/unit/kmx/042 - long context and split deadkeys.kmn	
+++ b/common/engine/keyboardprocessor/tests/unit/kmx/042 - long context and split deadkeys.kmn	
@@ -9,4 +9,6 @@ begin Unicode > use(Main)
 
 group(Main) using keys
 
+c Test 1: Test that we haven't split a deadkey code: UC_SENTINEL CODE_DEADKEY <deadkey_number>
+c         Here, looking at last char only: deadkey_number = U+0001
 U+0001 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefgh' + ' ' > 'FAIL'
diff --git a/common/engine/keyboardprocessor/tests/unit/kmx/kmx.cpp b/common/engine/keyboardprocessor/tests/unit/kmx/kmx.cpp
index b706b3a59c..bb7c255732 100644
--- a/common/engine/keyboardprocessor/tests/unit/kmx/kmx.cpp
+++ b/common/engine/keyboardprocessor/tests/unit/kmx/kmx.cpp
@@ -362,8 +362,8 @@ std::u16string parse_source_string(std::string const & s) {
         size_t n;
         std::string s1 = s.substr(p - s.begin(), 8);
         v = std::stoul(s1, &n, 16);
-        // Allow deadkey characters onward
-        assert(v >= CODE_ANY && v <= 0x10FFFF);
+        // Allow deadkey_number (U+0001) characters and onward
+        assert(v >= 0x0001 && v <= 0x10FFFF);
         p += n-1;
         if (v < 0x10000) {
           t += km_kbp_cp(v);