diff --git a/firmware/src/main.c b/firmware/src/main.c
index 3ef0c76..037a8f0 100644
--- a/firmware/src/main.c
+++ b/firmware/src/main.c
@@ -95,6 +95,9 @@ static const __flash uint8_t sym_t[] = { 0x0C, 0x0C, 0xFC, 0xFC, 0x0C, 0x0C,
 static const __flash uint8_t sym_u[] = { 0xFC, 0xFC, 0x00, 0x00, 0xFC, 0xFC,
                                          0x3F, 0x3F, 0x30, 0x30, 0x3F, 0x3F };
 
+static const __flash uint8_t sym_underscore[] = { 0x00, 0x00, 0x00, 0x00, 0x00,
+                                                  0x20, 0x20, 0x20, 0x20, 0x20 };
+
 static const __flash uint8_t sym_invalid[] = { 0x80, 0xE0, 0x98, 0xCC, 0x4C, 0x18, 0xE0, 0x80,
                                                0x01, 0x07, 0x1F, 0x24, 0x25, 0x1F, 0x07, 0x01};
 
@@ -140,7 +143,18 @@ static const struct symbol symbol_table[] = { SYM_ENTRY(sym_0),
                                               SYM_ENTRY(sym_r),
                                               SYM_ENTRY(sym_s),
                                               SYM_ENTRY(sym_t),
-                                              SYM_ENTRY(sym_u) };
+                                              SYM_ENTRY(sym_u),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_underscore),
+};
 
 enum input { cw, ccw, click, hold };