diff --git a/src/hci/keymap/keymap_al.c b/src/hci/keymap/keymap_al.c
index 4d279171f..6e14395a5 100644
--- a/src/hci/keymap/keymap_al.c
+++ b/src/hci/keymap/keymap_al.c
@@ -37,10 +37,15 @@ static struct keymap_key al_basic[] = {
 
 /** "al" AltGr remapping */
 static struct keymap_key al_altgr[] = {
+	{ 0x21, 0x7e },	/* '!' => '~' */
+	{ 0x26, 0x60 },	/* '&' => '`' */
 	{ 0x30, 0x7e },	/* '0' => '~' */
 	{ 0x31, 0x7e },	/* '1' => '~' */
 	{ 0x34, 0x7e },	/* '4' => '~' */
 	{ 0x37, 0x60 },	/* '7' => '`' */
+	{ 0x3a, 0x7e },	/* ':' => '~' */
+	{ 0x56, 0x60 },	/* 'V' => '`' */
+	{ 0x7c, 0x7e },	/* '|' => '~' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_cf.c b/src/hci/keymap/keymap_cf.c
index 434e3383c..55bbfc1a4 100644
--- a/src/hci/keymap/keymap_cf.c
+++ b/src/hci/keymap/keymap_cf.c
@@ -33,6 +33,7 @@ static struct keymap_key cf_altgr[] = {
 	{ 0x27, 0x7b },	/* '\'' => '{' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
 	{ 0x3b, 0x7e },	/* ';' => '~' */
+	{ 0x5c, 0x7d },	/* '\\' => '}' */
 	{ 0x60, 0x5c },	/* '`' => '\\' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_cz.c b/src/hci/keymap/keymap_cz.c
index fb072b117..08e9638e1 100644
--- a/src/hci/keymap/keymap_cz.c
+++ b/src/hci/keymap/keymap_cz.c
@@ -50,6 +50,9 @@ static struct keymap_key cz_basic[] = {
 
 /** "cz" AltGr remapping */
 static struct keymap_key cz_altgr[] = {
+	{ 0x21, 0x7e },	/* '!' => '~' */
+	{ 0x24, 0x7e },	/* '$' => '~' */
+	{ 0x29, 0x7e },	/* ')' => '~' */
 	{ 0x2c, 0x3c },	/* ',' => '<' */
 	{ 0x2e, 0x3e },	/* '.' => '>' */
 	{ 0x2f, 0x2a },	/* '/' => '*' */
@@ -60,10 +63,15 @@ static struct keymap_key cz_altgr[] = {
 	{ 0x37, 0x26 },	/* '7' => '&' */
 	{ 0x38, 0x2a },	/* '8' => '*' */
 	{ 0x39, 0x7b },	/* '9' => '{' */
+	{ 0x3a, 0x7e },	/* ':' => '~' */
 	{ 0x3b, 0x24 },	/* ';' => '$' */
+	{ 0x4b, 0x26 },	/* 'K' => '&' */
+	{ 0x58, 0x3e },	/* 'X' => '>' */
+	{ 0x5a, 0x3c },	/* 'Z' => '<' */
 	{ 0x61, 0x7e },	/* 'a' => '~' */
 	{ 0x62, 0x7b },	/* 'b' => '{' */
 	{ 0x63, 0x26 },	/* 'c' => '&' */
+	{ 0x66, 0x5b },	/* 'f' => '[' */
 	{ 0x67, 0x5d },	/* 'g' => ']' */
 	{ 0x6e, 0x7d },	/* 'n' => '}' */
 	{ 0x76, 0x40 },	/* 'v' => '@' */
diff --git a/src/hci/keymap/keymap_de.c b/src/hci/keymap/keymap_de.c
index bbd39520f..ca5e4a9a9 100644
--- a/src/hci/keymap/keymap_de.c
+++ b/src/hci/keymap/keymap_de.c
@@ -47,8 +47,13 @@ static struct keymap_key de_basic[] = {
 static struct keymap_key de_altgr[] = {
 	{ 0x2d, 0x5c },	/* '-' => '\\' */
 	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
 	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x3b, 0x7e },	/* ';' => '~' */
+	{ 0x5d, 0x7e },	/* ']' => '~' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0x7c, 0x7e },	/* '|' => '~' */
 	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_dk.c b/src/hci/keymap/keymap_dk.c
index 6d2e60aca..5b229024a 100644
--- a/src/hci/keymap/keymap_dk.c
+++ b/src/hci/keymap/keymap_dk.c
@@ -39,7 +39,14 @@ static struct keymap_key dk_basic[] = {
 static struct keymap_key dk_altgr[] = {
 	{ 0x30, 0x7d },	/* '0' => '}' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x34, 0x24 },	/* '4' => '$' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x3a, 0x7e },	/* ':' => '~' */
 	{ 0x3d, 0x7c },	/* '=' => '|' */
+	{ 0x5c, 0x7e },	/* '\\' => '~' */
+	{ 0x5d, 0x7e },	/* ']' => '~' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_es.c b/src/hci/keymap/keymap_es.c
index 614ca7b8b..93d87f2a0 100644
--- a/src/hci/keymap/keymap_es.c
+++ b/src/hci/keymap/keymap_es.c
@@ -37,14 +37,27 @@ static struct keymap_key es_basic[] = {
 
 /** "es" AltGr remapping */
 static struct keymap_key es_altgr[] = {
+	{ 0x22, 0x7b },	/* '"' => '{' */
 	{ 0x27, 0x7b },	/* '\'' => '{' */
+	{ 0x2b, 0x7e },	/* '+' => '~' */
+	{ 0x2d, 0x5c },	/* '-' => '\\' */
 	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x31, 0x7c },	/* '1' => '|' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x33, 0x23 },	/* '3' => '#' */
+	{ 0x34, 0x7e },	/* '4' => '~' */
 	{ 0x37, 0x7b },	/* '7' => '{' */
 	{ 0x38, 0x5b },	/* '8' => '[' */
 	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x3a, 0x7e },	/* ':' => '~' */
+	{ 0x3b, 0x7e },	/* ';' => '~' */
+	{ 0x3d, 0x7e },	/* '=' => '~' */
 	{ 0x5c, 0x7d },	/* '\\' => '}' */
+	{ 0x60, 0x5c },	/* '`' => '\\' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0x7c, 0x7e },	/* '|' => '~' */
+	{ 0x7e, 0x5c },	/* '~' => '\\' */
+	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_et.c b/src/hci/keymap/keymap_et.c
index f3eb02eab..4d763266f 100644
--- a/src/hci/keymap/keymap_et.c
+++ b/src/hci/keymap/keymap_et.c
@@ -35,8 +35,18 @@ static struct keymap_key et_basic[] = {
 
 /** "et" AltGr remapping */
 static struct keymap_key et_altgr[] = {
+	{ 0x26, 0x7b },	/* '&' => '{' */
+	{ 0x28, 0x5d },	/* '(' => ']' */
+	{ 0x29, 0x7d },	/* ')' => '}' */
+	{ 0x2a, 0x5b },	/* '*' => '[' */
 	{ 0x2d, 0x5c },	/* '-' => '\\' */
+	{ 0x30, 0x7d },	/* '0' => '}' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x34, 0x24 },	/* '4' => '$' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x5f, 0x5c },	/* '_' => '\\' */
 	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_fi.c b/src/hci/keymap/keymap_fi.c
index 622f06252..ac69813e8 100644
--- a/src/hci/keymap/keymap_fi.c
+++ b/src/hci/keymap/keymap_fi.c
@@ -38,6 +38,12 @@ static struct keymap_key fi_altgr[] = {
 	{ 0x2d, 0x5c },	/* '-' => '\\' */
 	{ 0x30, 0x7d },	/* '0' => '}' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x34, 0x24 },	/* '4' => '$' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x49, 0x7c },	/* 'I' => '|' */
+	{ 0x5d, 0x7e },	/* ']' => '~' */
 	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_fr.c b/src/hci/keymap/keymap_fr.c
index c002bf95a..ad797f876 100644
--- a/src/hci/keymap/keymap_fr.c
+++ b/src/hci/keymap/keymap_fr.c
@@ -68,9 +68,15 @@ static struct keymap_key fr_altgr[] = {
 	{ 0x2d, 0x5d },	/* '-' => ']' */
 	{ 0x30, 0x40 },	/* '0' => '@' */
 	{ 0x33, 0x23 },	/* '3' => '#' */
+	{ 0x34, 0x7b },	/* '4' => '{' */
 	{ 0x35, 0x5b },	/* '5' => '[' */
+	{ 0x36, 0x7c },	/* '6' => '|' */
+	{ 0x37, 0x60 },	/* '7' => '`' */
 	{ 0x38, 0x5c },	/* '8' => '\\' */
+	{ 0x3d, 0x7d },	/* '=' => '}' */
+	{ 0x5c, 0x60 },	/* '\\' => '`' */
 	{ 0x61, 0x40 },	/* 'a' => '@' */
+	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_hu.c b/src/hci/keymap/keymap_hu.c
index 8f2d70aac..d64baaebf 100644
--- a/src/hci/keymap/keymap_hu.c
+++ b/src/hci/keymap/keymap_hu.c
@@ -37,18 +37,36 @@ static struct keymap_key hu_basic[] = {
 
 /** "hu" AltGr remapping */
 static struct keymap_key hu_altgr[] = {
+	{ 0x21, 0x7e },	/* '!' => '~' */
+	{ 0x23, 0x5e },	/* '#' => '^' */
+	{ 0x26, 0x60 },	/* '&' => '`' */
+	{ 0x2c, 0x3b },	/* ',' => ';' */
 	{ 0x2e, 0x3e },	/* '.' => '>' */
 	{ 0x2f, 0x2a },	/* '/' => '*' */
+	{ 0x30, 0x7e },	/* '0' => '~' */
+	{ 0x31, 0x7e },	/* '1' => '~' */
 	{ 0x32, 0x5e },	/* '2' => '^' */
 	{ 0x33, 0x5e },	/* '3' => '^' */
+	{ 0x34, 0x7e },	/* '4' => '~' */
 	{ 0x37, 0x60 },	/* '7' => '`' */
 	{ 0x3b, 0x24 },	/* ';' => '$' */
+	{ 0x4b, 0x26 },	/* 'K' => '&' */
+	{ 0x58, 0x3e },	/* 'X' => '>' */
+	{ 0x5a, 0x3c },	/* 'Z' => '<' */
+	{ 0x62, 0x7b },	/* 'b' => '{' */
 	{ 0x63, 0x26 },	/* 'c' => '&' */
+	{ 0x66, 0x5b },	/* 'f' => '[' */
+	{ 0x67, 0x5d },	/* 'g' => ']' */
 	{ 0x6d, 0x3c },	/* 'm' => '<' */
+	{ 0x6e, 0x7d },	/* 'n' => '}' */
+	{ 0x71, 0x5c },	/* 'q' => '\\' */
 	{ 0x76, 0x40 },	/* 'v' => '@' */
+	{ 0x77, 0x7c },	/* 'w' => '|' */
 	{ 0x78, 0x23 },	/* 'x' => '#' */
 	{ 0x7a, 0x3e },	/* 'z' => '>' */
+	{ 0x7c, 0x7e },	/* '|' => '~' */
 	{ 0xdc, 0x3c },	/* Pseudo-'\\' => '<' */
+	{ 0xfc, 0x3e },	/* Pseudo-'|' => '>' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_it.c b/src/hci/keymap/keymap_it.c
index a55dafe6a..2511bb791 100644
--- a/src/hci/keymap/keymap_it.c
+++ b/src/hci/keymap/keymap_it.c
@@ -37,13 +37,19 @@ static struct keymap_key it_basic[] = {
 
 /** "it" AltGr remapping */
 static struct keymap_key it_altgr[] = {
+	{ 0x23, 0x7e },	/* '#' => '~' */
+	{ 0x27, 0x23 },	/* '\'' => '#' */
 	{ 0x2d, 0x60 },	/* '-' => '`' */
 	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
 	{ 0x39, 0x5d },	/* '9' => ']' */
 	{ 0x3b, 0x40 },	/* ';' => '@' */
 	{ 0x3d, 0x7e },	/* '=' => '~' */
+	{ 0x40, 0x7e },	/* '@' => '~' */
 	{ 0x5c, 0x60 },	/* '\\' => '`' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0x7c, 0x7e },	/* '|' => '~' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_lt.c b/src/hci/keymap/keymap_lt.c
index 5d6ee5a8c..a237b1d62 100644
--- a/src/hci/keymap/keymap_lt.c
+++ b/src/hci/keymap/keymap_lt.c
@@ -17,6 +17,10 @@ static struct keymap_key lt_basic[] = {
 
 /** "lt" AltGr remapping */
 static struct keymap_key lt_altgr[] = {
+	{ 0x22, 0x5e },	/* '"' => '^' */
+	{ 0x27, 0x5e },	/* '\'' => '^' */
+	{ 0x4b, 0x26 },	/* 'K' => '&' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_mt.c b/src/hci/keymap/keymap_mt.c
index 0a9a110b0..a95c5b4e8 100644
--- a/src/hci/keymap/keymap_mt.c
+++ b/src/hci/keymap/keymap_mt.c
@@ -22,6 +22,11 @@ static struct keymap_key mt_basic[] = {
 
 /** "mt" AltGr remapping */
 static struct keymap_key mt_altgr[] = {
+	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x5c, 0x60 },	/* '\\' => '`' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_no-latin1.c b/src/hci/keymap/keymap_no-latin1.c
index 63fe85548..1f4cc38d3 100644
--- a/src/hci/keymap/keymap_no-latin1.c
+++ b/src/hci/keymap/keymap_no-latin1.c
@@ -39,10 +39,15 @@ static struct keymap_key no_latin1_basic[] = {
 
 /** "no-latin1" AltGr remapping */
 static struct keymap_key no_latin1_altgr[] = {
+	{ 0x22, 0x5b },	/* '"' => '[' */
+	{ 0x27, 0x7b },	/* '\'' => '{' */
 	{ 0x30, 0x7d },	/* '0' => '}' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
 	{ 0x39, 0x5d },	/* '9' => ']' */
 	{ 0x5b, 0x7d },	/* '[' => '}' */
+	{ 0x7b, 0x5d },	/* '{' => ']' */
 	{ 0, 0 }
 };
 
diff --git a/src/hci/keymap/keymap_no.c b/src/hci/keymap/keymap_no.c
index 4b2f7268e..239e3aea5 100644
--- a/src/hci/keymap/keymap_no.c
+++ b/src/hci/keymap/keymap_no.c
@@ -41,6 +41,13 @@ static struct keymap_key no_basic[] = {
 static struct keymap_key no_altgr[] = {
 	{ 0x30, 0x7d },	/* '0' => '}' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x34, 0x24 },	/* '4' => '$' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x3a, 0x7e },	/* ':' => '~' */
+	{ 0x5c, 0x7e },	/* '\\' => '~' */
+	{ 0x5d, 0x7e },	/* ']' => '~' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_pt.c b/src/hci/keymap/keymap_pt.c
index f294e9563..75bf565ce 100644
--- a/src/hci/keymap/keymap_pt.c
+++ b/src/hci/keymap/keymap_pt.c
@@ -44,6 +44,7 @@ static struct keymap_key pt_altgr[] = {
 	{ 0x32, 0x40 },	/* '2' => '@' */
 	{ 0x37, 0x7b },	/* '7' => '{' */
 	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
 	{ 0, 0 }
 };
diff --git a/src/hci/keymap/keymap_se.c b/src/hci/keymap/keymap_se.c
index 6ca990444..9c6cf64a4 100644
--- a/src/hci/keymap/keymap_se.c
+++ b/src/hci/keymap/keymap_se.c
@@ -40,6 +40,11 @@ static struct keymap_key se_altgr[] = {
 	{ 0x2d, 0x5c },	/* '-' => '\\' */
 	{ 0x30, 0x7d },	/* '0' => '}' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x34, 0x24 },	/* '4' => '$' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x5d, 0x7e },	/* ']' => '~' */
 	{ 0x71, 0x40 },	/* 'q' => '@' */
 	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
 	{ 0, 0 }
diff --git a/src/hci/keymap/keymap_sg.c b/src/hci/keymap/keymap_sg.c
index 9a6db9cb4..2afe59c61 100644
--- a/src/hci/keymap/keymap_sg.c
+++ b/src/hci/keymap/keymap_sg.c
@@ -45,9 +45,11 @@ static struct keymap_key sg_basic[] = {
 
 /** "sg" AltGr remapping */
 static struct keymap_key sg_altgr[] = {
+	{ 0x27, 0x7b },	/* '\'' => '{' */
 	{ 0x32, 0x40 },	/* '2' => '@' */
 	{ 0x33, 0x23 },	/* '3' => '#' */
 	{ 0x37, 0x7c },	/* '7' => '|' */
+	{ 0x3d, 0x7e },	/* '=' => '~' */
 	{ 0x5c, 0x7d },	/* '\\' => '}' */
 	{ 0, 0 }
 };
diff --git a/src/util/genkeymap.py b/src/util/genkeymap.py
index 8df949612..632f71eda 100755
--- a/src/util/genkeymap.py
+++ b/src/util/genkeymap.py
@@ -33,6 +33,10 @@ import textwrap
 from typing import ClassVar, Optional
 
 
+BACKSPACE = chr(0x7f)
+"""Backspace character"""
+
+
 class KeyType(IntEnum):
     """Key types"""
 
@@ -174,7 +178,7 @@ class KeyLayout(UserDict[KeyModifiers, Sequence[Key]]):
             KeyModifiers.NONE: [(KEY_NON_US, ord('\\'))],
             KeyModifiers.SHIFT: [(KEY_NON_US, ord('|'))],
             # Treat Ctrl-Backspace as producing Backspace rather than Ctrl-H
-            KeyModifiers.CTRL: [(KEY_BACKSPACE, 0x7f)],
+            KeyModifiers.CTRL: [(KEY_BACKSPACE, ord(BACKSPACE))],
         },
         'il': {
             # Redefine some otherwise unreachable ASCII characters
@@ -200,11 +204,6 @@ class KeyLayout(UserDict[KeyModifiers, Sequence[Key]]):
         """Basic shifted keyboard layout"""
         return self[KeyModifiers.SHIFT]
 
-    @property
-    def altgr(self):
-        """AltGr keyboard layout"""
-        return self.get(KeyModifiers.ALTGR, self.unshifted)
-
     @classmethod
     def load(cls, name: str) -> KeyLayout:
         """Load keymap using 'loadkeys -b'"""
@@ -281,7 +280,7 @@ class BiosKeyLayout(KeyLayout):
         return inverse
 
 
-class KeymapKeys(UserDict[str, str]):
+class KeymapKeys(UserDict[str, Optional[str]]):
     """An ASCII character remapping"""
 
     @classmethod
@@ -312,7 +311,8 @@ class KeymapKeys(UserDict[str, str]):
                 self.ascii_name(source), self.ascii_name(target)
             )
             for source, target in self.items()
-            if ord(source) & ~BiosKeyLayout.KEY_PSEUDO != ord(target)
+            if target
+            and ord(source) & ~BiosKeyLayout.KEY_PSEUDO != ord(target)
         ) + '\t{ 0, 0 }\n}'
 
 
@@ -335,13 +335,12 @@ class Keymap:
         # Construct raw mapping from source ASCII to target ASCII
         raw = {source: self.target[key.modifiers][key.keycode].ascii
                for source, key in self.source.inverse.items()}
-        # Eliminate any null mappings, mappings that attempt to remap
-        # the backspace key, or identity mappings
+        # Eliminate any identity mappings, or mappings that attempt to
+        # remap the backspace key
         table = {source: target for source, target in raw.items()
-                 if target
-                 and ord(source) != 0x7f
-                 and ord(target) != 0x7f
-                 and source != target}
+                 if source != target
+                 and source != BACKSPACE
+                 and target != BACKSPACE}
         # Recursively delete any mappings that would produce
         # unreachable alphanumerics (e.g. the "il" keymap, which maps
         # away the whole lower-case alphabet)
@@ -354,8 +353,8 @@ class Keymap:
         # Sanity check: ensure that all numerics are reachable using
         # the same shift state
         digits = '1234567890'
-        unshifted = ''.join(table.get(x, x) for x in '1234567890')
-        shifted = ''.join(table.get(x, x) for x in '!@#$%^&*()')
+        unshifted = ''.join(table.get(x) or x for x in '1234567890')
+        shifted = ''.join(table.get(x) or x for x in '!@#$%^&*()')
         if digits not in (shifted, unshifted):
             raise ValueError("Inconsistent numeric remapping %s / %s" %
                              (unshifted, shifted))
@@ -365,21 +364,22 @@ class Keymap:
     def altgr(self) -> KeymapKeys:
         """AltGr remapping table"""
         # Construct raw mapping from source ASCII to target ASCII
-        raw = {source: self.target.altgr[key.keycode].ascii
-               for source, key in self.source.inverse.items()
-               if key.modifiers == KeyModifiers.NONE}
+        raw = {
+            source:
+            self.target.get((key.modifiers | KeyModifiers.ALTGR),
+                            self.target[key.modifiers])[key.keycode].ascii
+            for source, key in self.source.inverse.items()
+        }
         # Identify printable keys that are unreachable via the basic map
         basic = self.basic
         unmapped = set(x for x in basic.keys()
                        if x.isascii() and x.isprintable())
         remapped = set(basic.values())
         unreachable = unmapped - remapped
-        # Eliminate any null mappings, mappings for unprintable
-        # characters, or mappings for characters that are reachable
-        # via the basic map
+        # Eliminate any mappings for unprintable characters, or
+        # mappings for characters that are reachable via the basic map
         table = {source: target for source, target in raw.items()
                  if source.isprintable()
-                 and target
                  and target in unreachable}
         # Check that all characters are now reachable
         unreachable -= set(table.values())