diff --git a/src/fontra_rcjk/backend_fs.py b/src/fontra_rcjk/backend_fs.py
index 4221bcb..b5108b2 100644
--- a/src/fontra_rcjk/backend_fs.py
+++ b/src/fontra_rcjk/backend_fs.py
@@ -164,7 +164,9 @@ async def getGlyph(self, glyphName: str) -> VariableGlyph | None:
             layerGlyphs = self._getLayerGlyphs(glyphName)
         except KeyError:
             return None
-        return buildVariableGlyphFromLayerGlyphs(layerGlyphs)
+        return buildVariableGlyphFromLayerGlyphs(
+            layerGlyphs, self.designspace.axes.axes
+        )
 
     def _getLayerGlyphs(self, glyphName):
         layerGlyphs = self._tempGlyphCache.get(glyphName)
diff --git a/src/fontra_rcjk/backend_mysql.py b/src/fontra_rcjk/backend_mysql.py
index dc555c4..04b1b25 100644
--- a/src/fontra_rcjk/backend_mysql.py
+++ b/src/fontra_rcjk/backend_mysql.py
@@ -256,8 +256,11 @@ async def getGlyph(self, glyphName: str) -> VariableGlyph | None:
             return None
         glyph = self._readGlyphFromCacheDir(glyphName)
         if glyph is None:
+            designspace = await self._getDesignspace()
             layerGlyphs = await self._getLayerGlyphs(glyphName)
-            glyph = buildVariableGlyphFromLayerGlyphs(layerGlyphs)
+            glyph = buildVariableGlyphFromLayerGlyphs(
+                layerGlyphs, designspace.axes.axes
+            )
             self._writeGlyphToCacheDir(glyphName, glyph)
         return glyph
 
diff --git a/src/fontra_rcjk/base.py b/src/fontra_rcjk/base.py
index 1422372..0f62dff 100644
--- a/src/fontra_rcjk/base.py
+++ b/src/fontra_rcjk/base.py
@@ -22,6 +22,7 @@
 from fontTools.misc.transform import DecomposedTransform
 from fontTools.ufoLib.filenames import illegalCharacters
 from fontTools.ufoLib.glifLib import readGlyphFromString, writeGlyphToString
+from fontTools.varLib.models import piecewiseLinearMap
 
 FONTRA_STATUS_KEY = "fontra.development.status"
 
@@ -119,7 +120,7 @@ def cleanupAxis(axisDict):
     return GlyphAxis(**axisDict)
 
 
-def buildVariableGlyphFromLayerGlyphs(layerGlyphs) -> VariableGlyph:
+def buildVariableGlyphFromLayerGlyphs(layerGlyphs, fontAxes) -> VariableGlyph:
     layers = {
         layerName: Layer(glyph=glyph.toStaticGlyph())
         for layerName, glyph in layerGlyphs.items()
@@ -219,13 +220,52 @@ def buildVariableGlyphFromLayerGlyphs(layerGlyphs) -> VariableGlyph:
             for layerName, layer in layers.items()
         }
 
-    return VariableGlyph(
+    glyph = VariableGlyph(
         name=defaultGlyph.name,
         axes=defaultGlyph.axes,
         sources=sources,
         layers=layers,
     )
 
+    if not defaultGlyph.lib.get("robocjk.localAxes.behavior.2024", False):
+        upconvertShadowAxes(glyph, fontAxes)
+
+    return glyph
+
+
+def upconvertShadowAxes(glyph, fontAxes):
+    fontAxisNames = {axis.name for axis in fontAxes}
+    glyphAxisNames = {axis.name for axis in glyph.axes}
+    if fontAxisNames.isdisjoint(glyphAxisNames):
+        return
+
+    glyphAxesByName = {axis.name: axis for axis in glyph.axes}
+
+    for fontAxis in fontAxes:
+        axisName = fontAxis.name
+        fontAxisTuple = (fontAxis.minValue, fontAxis.defaultValue, fontAxis.maxValue)
+        if fontAxis.mapping:
+            mapping = dict(fontAxis.mapping)
+            fontAxisTuple = tuple(piecewiseLinearMap(v, mapping) for v in fontAxisTuple)
+
+        glyphAxis = glyphAxesByName.get(axisName)
+        if glyphAxis is None:
+            continue
+
+        mapping = dict(
+            zip(
+                [glyphAxis.minValue, glyphAxis.defaultValue, glyphAxis.maxValue],
+                fontAxisTuple,
+            )
+        )
+
+        for source in glyph.sources:
+            v = source.location.get(axisName)
+            if v is not None:
+                source.location[axisName] = piecewiseLinearMap(v, mapping)
+
+    glyph.axes = [axis for axis in glyph.axes if axis.name not in fontAxisNames]
+
 
 def buildVariableComponentsFromLibComponents(deepComponents, dcNames):
     components = []
@@ -359,6 +399,9 @@ def buildLayerGlyphsFromVariableGlyph(
     # Get rid of legacy data
     defaultGlyph.lib.pop("fontra.layerNames", None)
 
+    # Mark that we shouldn't try to upconvert shadow axes
+    defaultGlyph.lib["robocjk.localAxes.behavior.2024"] = True
+
     return layerGlyphs
 
 
diff --git a/tests/data/figArnaud.rcjk/characterGlyph/a.glif b/tests/data/figArnaud.rcjk/characterGlyph/a.glif
index 7ffd2f8..12e54e3 100644
--- a/tests/data/figArnaud.rcjk/characterGlyph/a.glif
+++ b/tests/data/figArnaud.rcjk/characterGlyph/a.glif
@@ -15,6 +15,8 @@ some note
   </outline>
   <lib>
     <dict>
+      <key>robocjk.localAxes.behavior.2024</key>
+      <true/>
       <key>robocjk.status</key>
       <integer>0</integer>
       <key>robocjk.variationGlyphs</key>
diff --git a/tests/data/figArnaud.rcjk/characterGlyph/uni0030.glif b/tests/data/figArnaud.rcjk/characterGlyph/uni0030.glif
index 734ab1f..af42200 100644
--- a/tests/data/figArnaud.rcjk/characterGlyph/uni0030.glif
+++ b/tests/data/figArnaud.rcjk/characterGlyph/uni0030.glif
@@ -11,19 +11,6 @@
     <dict>
       <key>public.markColor</key>
       <string>1,0,0,1</string>
-      <key>robocjk.axes</key>
-      <array>
-        <dict>
-          <key>defaultValue</key>
-          <integer>0</integer>
-          <key>maxValue</key>
-          <integer>1</integer>
-          <key>minValue</key>
-          <integer>0</integer>
-          <key>name</key>
-          <string>wght</string>
-        </dict>
-      </array>
       <key>robocjk.deepComponents</key>
       <array>
         <dict>
@@ -55,6 +42,8 @@
           </dict>
         </dict>
       </array>
+      <key>robocjk.localAxes.behavior.2024</key>
+      <true/>
       <key>robocjk.status</key>
       <integer>0</integer>
       <key>robocjk.variationGlyphs</key>
@@ -96,7 +85,7 @@
           <key>location</key>
           <dict>
             <key>wght</key>
-            <real>1.0</real>
+            <real>700.0</real>
           </dict>
           <key>on</key>
           <true/>
diff --git a/tests/test_font.py b/tests/test_font.py
index 7c09821..ed29975 100644
--- a/tests/test_font.py
+++ b/tests/test_font.py
@@ -154,9 +154,7 @@
     (
         "rcjk",
         {
-            "axes": [
-                {"defaultValue": 0.0, "maxValue": 1.0, "minValue": 0.0, "name": "wght"}
-            ],
+            "axes": [],
             "name": "uni0031",
             "sources": [
                 {
@@ -167,7 +165,7 @@
                 },
                 {
                     "name": "wght",
-                    "location": {"wght": 1.0},
+                    "location": {"wght": 700},
                     "layerName": "wght",
                     "customData": {"fontra.development.status": 0},
                 },
@@ -482,6 +480,8 @@ def writableTestFont(tmpdir):
     "  </outline>",
     "  <lib>",
     "    <dict>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "      <key>robocjk.variationGlyphs</key>",
@@ -527,6 +527,8 @@ def writableTestFont(tmpdir):
     "  </outline>",
     "  <lib>",
     "    <dict>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "      <key>robocjk.variationGlyphs</key>",
@@ -592,6 +594,8 @@ async def test_putGlyph(writableTestFont):
     "  </outline>",
     "  <lib>",
     "    <dict>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "      <key>xyz.fontra.something.nothing</key>",
@@ -644,6 +648,8 @@ async def test_delete_source_layer(writableTestFont):
     "          <string>wght</string>",
     "        </dict>",
     "      </array>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "      <key>robocjk.variationGlyphs</key>",
@@ -752,6 +758,8 @@ async def test_write_roundtrip(writableTestFont, glyphName):
     "  </outline>",
     "  <lib>",
     "    <dict>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "      <key>robocjk.variationGlyphs</key>",
@@ -850,6 +858,8 @@ async def test_bad_layer_name(writableTestFont):
     "    <dict>",
     "      <key>public.markColor</key>",
     "      <string>1,0,0,1</string>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "      <key>xyz.fontra.test</key>",
@@ -977,6 +987,8 @@ async def test_readMixClassicAndVariableComponents():
     "          </dict>",
     "        </dict>",
     "      </array>",
+    "      <key>robocjk.localAxes.behavior.2024</key>",
+    "      <true/>",
     "      <key>robocjk.status</key>",
     "      <integer>0</integer>",
     "    </dict>",