diff --git a/fontbe/src/os2.rs b/fontbe/src/os2.rs
index 37965e129..04d7cc09f 100644
--- a/fontbe/src/os2.rs
+++ b/fontbe/src/os2.rs
@@ -533,20 +533,27 @@ impl Work<Context, AnyWorkId, Error> for Os2Work {
     fn exec(&self, context: &Context) -> Result<(), Error> {
         let static_metadata = context.ir.static_metadata.get();
 
-        // We set the OS/2.us{Weight,Width}Class to the default value of 'wght'/'wdth' axes
+        // If the source doesn't explicitly assign a value then
+        // set the OS/2.us{Weight,Width}Class to the default value of 'wght'/'wdth' axes
         // in the same way fontmake does when building a VF:
         // https://github.com/fonttools/fonttools/blob/770917d8/Lib/fontTools/varLib/__init__.py#L1016-L1032
-        let default_wght = static_metadata
-            .axis(&Tag::new(b"wght"))
-            .map(|axis| axis.default.into_inner().0)
-            .unwrap_or(400.0);
-        let us_weight_class: u16 = default_wght.clamp(1.0, 1000.0).ot_round();
-
-        let default_wdth = static_metadata
-            .axis(&Tag::new(b"wdth"))
-            .map(|axis| axis.default.into_inner().0)
-            .unwrap_or(100.0);
-        let us_width_class = WidthClass::nearest(default_wdth) as u16;
+        let us_x_class = |misc_value: Option<u16>, axis_tag, default, clamp: fn(f64) -> u16| {
+            misc_value.unwrap_or_else(|| {
+                clamp(
+                    static_metadata
+                        .axis(&Tag::new(axis_tag))
+                        .map(|axis| axis.default.into_inner().0)
+                        .unwrap_or(default),
+                )
+            })
+        };
+        let us_weight_class =
+            us_x_class(static_metadata.misc.us_weight_class, b"wght", 400.0, |v| {
+                v.clamp(1.0, 1000.0).ot_round()
+            });
+        let us_width_class = us_x_class(static_metadata.misc.us_width_class, b"wdth", 100.0, |v| {
+            WidthClass::nearest(v) as u16
+        });
 
         let metrics = context
             .ir
diff --git a/fontc/src/lib.rs b/fontc/src/lib.rs
index 487269e67..738fb7740 100644
--- a/fontc/src/lib.rs
+++ b/fontc/src/lib.rs
@@ -1291,6 +1291,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn prefers_explicit_os_x_class() {
+        let result = TestCompile::compile_source("fontinfo.designspace");
+        let font = result.font();
+        let os2 = font.os2().unwrap();
+
+        assert_eq!((800, 8), (os2.us_weight_class(), os2.us_width_class(),),);
+    }
+
     #[test]
     fn glyphs_app_ir_categories() {
         let result = TestCompile::compile_source("glyphs3/Oswald-glyph-categories.glyphs");
diff --git a/fontir/src/ir.rs b/fontir/src/ir.rs
index 5f27dd9b0..bde03336a 100644
--- a/fontir/src/ir.rs
+++ b/fontir/src/ir.rs
@@ -137,6 +137,15 @@ pub struct MiscMetadata {
     // Allows source to explicitly control bits. <https://github.com/googlefonts/fontc/issues/1027>
     pub codepage_range_bits: Option<HashSet<u32>>,
     pub meta_table: Option<MetaTableValues>,
+
+    /// <https://learn.microsoft.com/en-us/typography/opentype/spec/os2#usweightclass>
+    ///
+    /// If empty and there is a weight axis OS/2 will use the weight default
+    pub us_weight_class: Option<u16>,
+    /// <https://learn.microsoft.com/en-us/typography/opentype/spec/os2#uswidthclass>
+    ///
+    /// If empty and there is a width axis OS/2 will use the width default
+    pub us_width_class: Option<u16>,
 }
 
 /// PANOSE bytes
@@ -498,6 +507,8 @@ impl StaticMetadata {
                 unicode_range_bits: None,
                 codepage_range_bits: None,
                 meta_table: None,
+                us_weight_class: None,
+                us_width_class: None,
             },
         })
     }
@@ -1961,6 +1972,8 @@ mod tests {
                 unicode_range_bits: None,
                 codepage_range_bits: None,
                 meta_table: None,
+                us_weight_class: None,
+                us_width_class: None,
             },
             number_values: Default::default(),
         }
diff --git a/resources/testdata/FontInfo-Regular.ufo/fontinfo.plist b/resources/testdata/FontInfo-Regular.ufo/fontinfo.plist
index e75e8de16..668f67712 100644
--- a/resources/testdata/FontInfo-Regular.ufo/fontinfo.plist
+++ b/resources/testdata/FontInfo-Regular.ufo/fontinfo.plist
@@ -34,5 +34,9 @@
     <integer>-290</integer>
     <key>openTypeHheaLineGap</key>
     <integer>43</integer>
+    <key>openTypeOS2WeightClass</key>
+    <integer>800</integer>
+    <key>openTypeOS2WidthClass</key>
+    <integer>8</integer>
   </dict>
 </plist>
diff --git a/ufo2fontir/src/source.rs b/ufo2fontir/src/source.rs
index 55de154d4..6a5b39a10 100644
--- a/ufo2fontir/src/source.rs
+++ b/ufo2fontir/src/source.rs
@@ -604,6 +604,7 @@ fn names(font_info: &norad::FontInfo) -> HashMap<NameKey, String> {
             .into()
         }),
     );
+
     builder.add_if_present(NameId::UNIQUE_ID, &font_info.open_type_name_unique_id);
     builder.add_if_present(NameId::VERSION_STRING, &font_info.open_type_name_version);
     builder.add_if_present(NameId::POSTSCRIPT_NAME, &font_info.postscript_font_name);
@@ -818,6 +819,13 @@ impl Work<Context, WorkId, Error> for StaticMetadataWork {
                 })?;
         }
 
+        static_metadata.misc.us_weight_class = font_info_at_default
+            .open_type_os2_weight_class
+            .map(|v| v as u16);
+        static_metadata.misc.us_width_class = font_info_at_default
+            .open_type_os2_width_class
+            .map(|v| v as u16);
+
         // <https://github.com/googlefonts/glyphsLib/blob/cb8a4a914b0a33431f0a77f474bf57eec2f19bcc/Lib/glyphsLib/builder/custom_params.py#L1117-L1119>
         static_metadata.misc.fs_type = Some(
             font_info_at_default