diff --git a/libs/libc/misc/lib_slcddecode.c b/libs/libc/misc/lib_slcddecode.c
index 6ff5580ea6c..df3f5221123 100644
--- a/libs/libc/misc/lib_slcddecode.c
+++ b/libs/libc/misc/lib_slcddecode.c
@@ -87,7 +87,7 @@ static uint8_t slcd_nibble(uint8_t ascii)
     }
   else
     {
-      return ascii - 'a';
+      return ascii - 'a' + 10;
     }
 }
 
diff --git a/libs/libc/misc/lib_slcdencode.c b/libs/libc/misc/lib_slcdencode.c
index 2e512d4b23f..f47b03f518e 100644
--- a/libs/libc/misc/lib_slcdencode.c
+++ b/libs/libc/misc/lib_slcdencode.c
@@ -60,7 +60,7 @@ static uint8_t slcd_nibble(uint8_t binary)
     }
   else
     {
-      return 'a' + binary;
+      return 'a' + binary - 10;
     }
 }