diff --git a/src/,,config_custom.s b/src/,,config_custom.s
index 4ec8112f..b01cae6c 100644
--- a/src/,,config_custom.s
+++ b/src/,,config_custom.s
@@ -88,11 +88,7 @@
 
 ;; #CONFIG# PROGRAMMABLE_KEYS          YES
 
-;; #CONFIG# KEYCMD_RUN                 YES
-!macro CONFIG_KEYCMD_RUN  {
-	!byte $5F
-	!pet "l"
-}
+;; #CONFIG# KEYCMD_RUN                 "\5FL"
 
 ;; #CONFIG# KEYCMD_F1                  "@8$"
 ;; #CONFIG# KEYCMD_F2                  "LOAD"
diff --git a/src/,,config_generic.s b/src/,,config_generic.s
index 97644990..970f7cde 100644
--- a/src/,,config_generic.s
+++ b/src/,,config_generic.s
@@ -76,11 +76,7 @@
 
 ;; #CONFIG# PROGRAMMABLE_KEYS          YES
 
-;; #CONFIG# KEYCMD_RUN                 YES
-!macro CONFIG_KEYCMD_RUN  {
-	!byte $5F
-	!pet "l"
-}
+;; #CONFIG# KEYCMD_RUN                 "\5FL"
 
 ;; #CONFIG# KEYCMD_F1                  "@8$"
 ;; #CONFIG# KEYCMD_F2                  "LOAD"
diff --git a/src/,,config_mega65.s b/src/,,config_mega65.s
index 26c4586c..54431853 100644
--- a/src/,,config_mega65.s
+++ b/src/,,config_mega65.s
@@ -56,10 +56,7 @@
 
 ;; #CONFIG# PROGRAMMABLE_KEYS          YES
 
-;; #CONFIG# KEYCMD_RUN                 YES
-!macro CONFIG_KEYCMD_RUN  {
-	!byte $5F
-	!pet "l" }
+;; #CONFIG# KEYCMD_RUN                 "RUN"
 
 ;; #CONFIG# KEYCMD_F1                  "@8$"
 ;; #CONFIG# KEYCMD_F2                  "LOAD"
@@ -72,9 +69,9 @@
 
 ;; #CONFIG# KEYCMD_HELP                "LIST"
 
-;; #CONFIG# KEYCMD_F9                  "REM F9"
+;; #CONFIG# KEYCMD_F9                  "\5FL"
 ;; #CONFIG# KEYCMD_F10                 "REM F10"
-;; #CONFIG# KEYCMD_F11                 "REM F11"
+;; #CONFIG# KEYCMD_F11                 "\5FH"
 ;; #CONFIG# KEYCMD_F12                 "REM F12"
 ;; #CONFIG# KEYCMD_F13                 "REM F13"
 ;; #CONFIG# KEYCMD_F14                 "REM F14"
diff --git a/src/,,config_testing.s b/src/,,config_testing.s
index 4deed9b5..fb714a01 100644
--- a/src/,,config_testing.s
+++ b/src/,,config_testing.s
@@ -76,11 +76,7 @@
 
 ;; #CONFIG# PROGRAMMABLE_KEYS          YES
 
-;; #CONFIG# KEYCMD_RUN                 YES
-!macro CONFIG_KEYCMD_RUN  {
-	!byte $5F
-	!pet "l"
-}
+;; #CONFIG# KEYCMD_RUN                 "\5FL"
 
 ;; #CONFIG# KEYCMD_F1                  "@8$"
 ;; #CONFIG# KEYCMD_F2                  "LOAD"
diff --git a/src/,,config_ultimate64.s b/src/,,config_ultimate64.s
index 290a927d..edd352c7 100644
--- a/src/,,config_ultimate64.s
+++ b/src/,,config_ultimate64.s
@@ -66,11 +66,7 @@
 
 ;; #CONFIG# PROGRAMMABLE_KEYS          YES
 
-;; #CONFIG# KEYCMD_RUN                 YES
-!macro CONFIG_KEYCMD_RUN  {
-	!byte $5F
-	!pet "l"
-}
+;; #CONFIG# KEYCMD_RUN                 "\5FL"
 
 ;; #CONFIG# KEYCMD_F1                  "@8$"
 ;; #CONFIG# KEYCMD_F2                  "LOAD"
diff --git a/tools/build_segment.cc b/tools/build_segment.cc
index beebbe35..c49cc383 100644
--- a/tools/build_segment.cc
+++ b/tools/build_segment.cc
@@ -849,9 +849,18 @@ void SourceFile::preprocessLine_Config(const std::list<std::string> &tokens, std
                 if ((line.size() <= ++pos) || (line[pos] == '\n')) ERROR("syntax error, unfinished string in '#CONFIG#'");
                 byte = line[pos];
             };
+            auto byteToNibble = [&byte]() -> uint8_t
+            {
+                if (byte >= '0' && byte <= '9') return byte - '0';
+                if (byte >= 'a' && byte <= 'f') return byte - 'a' + 10;
+                if (byte >= 'A' && byte <= 'F') return byte - 'A' + 10;
+
+                ERROR("syntax error, improper 2-digit hex value in '#CONFIG#'");
+                return 0;
+            };
 
             advance();
-            
+
             // Convert string from ASCII to PETSCII
 
             if (byte == '"') break;
@@ -862,10 +871,15 @@ void SourceFile::preprocessLine_Config(const std::list<std::string> &tokens, std
                 if (byte == '"')
                 {
                     configEntries[lineNum].valBlob.push_back(byte);
-                    continue;
                 }
+                else
+                {
+                    uint8_t val = byteToNibble() * 16;
+                    advance();
+                    val += byteToNibble(); 
 
-                // XXX handle hex values
+                    configEntries[lineNum].valBlob.push_back(val);
+                }
             }
             else if ((byte >= 0x20 && byte <= 0x5B) || byte == 0x5D) configEntries[lineNum].valBlob.push_back(byte);
             else ERROR("syntax error, invalid character in string in '#CONFIG#'");