diff --git a/metrics/extract_ttfs.py b/metrics/extract_ttfs.py
index 4b80e5afa..edcf0da5a 100755
--- a/metrics/extract_ttfs.py
+++ b/metrics/extract_ttfs.py
@@ -84,7 +84,7 @@ def main():
                     italic = 0
                     skew = 0
 
-                start_json[font][ord(char)] = {
+                start_json[font][str(ord(char))] = {
                     "height": height / fontInfo.em,
                     "depth": depth / fontInfo.em,
                     "italic": italic,
diff --git a/metrics/mapping.pl b/metrics/mapping.pl
index 2b6cf53f2..1a346657b 100755
--- a/metrics/mapping.pl
+++ b/metrics/mapping.pl
@@ -135,8 +135,6 @@ $map{cmmi10} = {
     0x2E => 0x25B9,         # \triangleright
     0x2F => 0x25C3,         # \triangleleft
 
-    0x3A => 0x2E,           # .
-    0x3B => 0x2C,           # ,
     0x3C => 0x3C,           # <
     0x3D => 0x2215,         # /
     0x3E => 0x3E,           # >
@@ -148,16 +146,19 @@ $map{cmmi10} = {
     0x5F => 0x2322,         # \frown
     0x60 => 0x2113,         # \ell
 
-    0x7B => 0x131,          # \imath
-    0x7C => 0x237,          # \jmath
     0x7D => 0x2118,         # \wp
     0x7E => [0x20D7,-653,0],# \vec
+  ],
+
+  "Main-Italic" => [
+    0x7B => 0x131,          # \imath
+    0x7C => 0x237,          # \jmath
   ]
 };
 
 $map{cmsy10} = {
   "Main-Regular" => [
-    [0,1] => 0x2212,        # -
+    0 => 0x2212,            # -
     1 => 0x22C5,            # \cdot
     2 => 0xD7,              # \times
     3 => 0x2217,            # \ast
@@ -425,8 +426,6 @@ $map{cmti10} = {
     [7,8] => 0x3A5,         # \Upsilon, \Phi
     [9,0xA] => 0x3A8,       # \Psi, \Omega
 
-    0x10 => 0x131,          # \imath (roman)
-    0x11 => 0x237,          # \jmath (roman)
     0x12 => [0x300,-511,0], # \grave (combining)
     0x13 => [0x301,-511,0], # \acute (combining)
     0x14 => [0x30C,-511,0], # \check (combining)
@@ -557,8 +556,6 @@ $map{cmmib10} = {
     0x2E => 0x25B9,         # \triangleright
     0x2F => 0x25C3,         # \triangleleft
 
-    0x3A => 0x2E,           # .
-    0x3B => 0x2C,           # ,
     0x3C => 0x3C,           # <
     0x3D => 0x2215,         # /
     0x3E => 0x3E,           # >
@@ -571,8 +568,6 @@ $map{cmmib10} = {
     0x60 => 0x2113,         # \ell
     0x68 => 0x210F,         # \hbar (bar added below)
 
-    0x7B => 0x131,          # \imath
-    0x7C => 0x237,          # \jmath
     0x7D => 0x2118,         # \wp
     0x7E => [0x20D7,-729,0],# \vec
   ],
@@ -580,7 +575,7 @@ $map{cmmib10} = {
 
 $map{cmbsy10} = {
   "Main-Bold" => [
-    [0,1] => 0x2212,        # -
+    0 => 0x2212,            # -
     1 => 0x22C5,            # \cdot
     2 => 0xD7,              # \times
     3 => 0x2217,            # \ast
@@ -973,6 +968,12 @@ sub add_to_output {
         "yshift" => $yshift
     };
 
+    if (defined($output{$mjfont}{$to})) {
+        print STDERR "Duplicate mapping $to for $mjfont: " .
+            $output{$mjfont}{$to}{font} . ":" .
+            $output{$mjfont}{$to}{char} . " vs. $cmfont:$from\n";
+        die "Duplicate mapping!"; # disable this line to see all of them
+    }
     $output{$mjfont}{$to} = $data;
 }
 
diff --git a/src/fontMetricsData.json b/src/fontMetricsData.json
index bffae4dc8..caa5ec522 100644
--- a/src/fontMetricsData.json
+++ b/src/fontMetricsData.json
@@ -599,8 +599,8 @@
   "122": {"depth": 0.0, "height": 0.43056, "italic": 0.12292, "skew": 0.0},
   "126": {"depth": 0.35, "height": 0.31786, "italic": 0.11585, "skew": 0.0},
   "163": {"depth": 0.0, "height": 0.69444, "italic": 0.0, "skew": 0.0},
-  "305": {"depth": 0.0, "height": 0.43056, "italic": 0.07671, "skew": 0.0},
-  "567": {"depth": 0.19444, "height": 0.43056, "italic": 0.03736, "skew": 0.0},
+  "305": {"depth": 0.0, "height": 0.43056, "italic": 0.0, "skew": 0.02778},
+  "567": {"depth": 0.19444, "height": 0.43056, "italic": 0.0, "skew": 0.08334},
   "768": {"depth": 0.0, "height": 0.69444, "italic": 0.0, "skew": 0.0},
   "769": {"depth": 0.0, "height": 0.69444, "italic": 0.09694, "skew": 0.0},
   "770": {"depth": 0.0, "height": 0.69444, "italic": 0.06646, "skew": 0.0},
@@ -736,8 +736,8 @@
   "180": {"depth": 0.0, "height": 0.69444, "italic": 0.0, "skew": 0.0},
   "215": {"depth": 0.08333, "height": 0.58333, "italic": 0.0, "skew": 0.0},
   "247": {"depth": 0.08333, "height": 0.58333, "italic": 0.0, "skew": 0.0},
-  "305": {"depth": 0.0, "height": 0.43056, "italic": 0.0, "skew": 0.02778},
-  "567": {"depth": 0.19444, "height": 0.43056, "italic": 0.0, "skew": 0.08334},
+  "305": {"depth": 0.0, "height": 0.43056, "italic": 0.0, "skew": 0.0},
+  "567": {"depth": 0.19444, "height": 0.43056, "italic": 0.0, "skew": 0.0},
   "710": {"depth": 0.0, "height": 0.69444, "italic": 0.0, "skew": 0.0},
   "711": {"depth": 0.0, "height": 0.62847, "italic": 0.0, "skew": 0.0},
   "713": {"depth": 0.0, "height": 0.56778, "italic": 0.0, "skew": 0.0},