diff --git a/src/fontra/backends/designspace.py b/src/fontra/backends/designspace.py
index f9ea2a4400..80aadb635c 100644
--- a/src/fontra/backends/designspace.py
+++ b/src/fontra/backends/designspace.py
@@ -178,9 +178,12 @@ def updateGlyphSetContents(self, glyphSet):
         for glyphName, fileName in glyphSet.contents.items():
             glifFileNames[fileName] = glyphName
 
-    async def getGlyphMap(self):
+    async def getGlyphMap(self) -> dict[str, list[int]]:
         return dict(self.glyphMap)
 
+    async def putGlyphMap(self, value: dict[str, list[int]]) -> None:
+        pass
+
     async def getGlyph(self, glyphName: str) -> VariableGlyph | None:
         if glyphName not in self.glyphMap:
             return None
@@ -538,7 +541,7 @@ async def deleteGlyph(self, glyphName):
         del self.glyphMap[glyphName]
         self.savedGlyphModificationTimes[glyphName] = None
 
-    async def getGlobalAxes(self):
+    async def getGlobalAxes(self) -> list[GlobalAxis | GlobalDiscreteAxis]:
         return self.axes
 
     async def putGlobalAxes(self, axes):
@@ -561,10 +564,20 @@ async def putGlobalAxes(self, axes):
         self.updateAxisInfo()
         self.loadUFOLayers()
 
-    async def getUnitsPerEm(self):
+    async def getUnitsPerEm(self) -> int:
         return self.defaultFontInfo.unitsPerEm
 
-    async def getCustomData(self):
+    async def putUnitsPerEm(self, value: int) -> None:
+        del self.defaultFontInfo
+        ufoPaths = sorted(set(self.ufoLayers.iterAttrs("path")))
+        for ufoPath in ufoPaths:
+            reader = self.ufoManager.getReader(ufoPath)
+            info = UFOFontInfo()
+            reader.readInfo(info)
+            info.unitsPerEm = value
+            reader.writeInfo(info)
+
+    async def getCustomData(self) -> dict[str, Any]:
         return deepcopy(self.dsDoc.lib)
 
     async def putCustomData(self, lib):
diff --git a/src/fontra/backends/fontra.py b/src/fontra/backends/fontra.py
index 45cf845ebd..4d772694b6 100644
--- a/src/fontra/backends/fontra.py
+++ b/src/fontra/backends/fontra.py
@@ -7,9 +7,16 @@
 from copy import deepcopy
 from dataclasses import dataclass, field
 from os import PathLike
-from typing import Callable
-
-from fontra.core.classes import Font, VariableGlyph, structure, unstructure
+from typing import Any, Callable
+
+from fontra.core.classes import (
+    Font,
+    GlobalAxis,
+    GlobalDiscreteAxis,
+    VariableGlyph,
+    structure,
+    unstructure,
+)
 from fontra.core.protocols import WritableFontBackend
 
 from .filenames import stringToFileName
@@ -66,16 +73,19 @@ def close(self):
     def flush(self):
         self._scheduler.flush()
 
-    async def getUnitsPerEm(self):
+    async def getUnitsPerEm(self) -> int:
         return self.fontData.unitsPerEm
 
     async def putUnitsPerEm(self, unitsPerEm):
         self.fontData.unitsPerEm = unitsPerEm
         self._scheduler.schedule(self._writeFontData)
 
-    async def getGlyphMap(self):
+    async def getGlyphMap(self) -> dict[str, list[int]]:
         return dict(self.glyphMap)
 
+    async def putGlyphMap(self, value: dict[str, list[int]]) -> None:
+        pass
+
     async def getGlyph(self, glyphName: str) -> VariableGlyph | None:
         try:
             jsonSource = self.getGlyphData(glyphName)
@@ -95,14 +105,14 @@ async def putGlyph(
     async def deleteGlyph(self, glyphName):
         self.glyphMap.pop(glyphName, None)
 
-    async def getGlobalAxes(self):
+    async def getGlobalAxes(self) -> list[GlobalAxis | GlobalDiscreteAxis]:
         return deepcopy(self.fontData.axes)
 
     async def putGlobalAxes(self, axes):
         self.fontData.axes = deepcopy(axes)
         self._scheduler.schedule(self._writeFontData)
 
-    async def getCustomData(self):
+    async def getCustomData(self) -> dict[str, Any]:
         return deepcopy(self.fontData.customData)
 
     async def putCustomData(self, customData):
diff --git a/src/fontra/backends/opentype.py b/src/fontra/backends/opentype.py
index ff748a700f..ea02b2b243 100644
--- a/src/fontra/backends/opentype.py
+++ b/src/fontra/backends/opentype.py
@@ -1,4 +1,5 @@
 from os import PathLike
+from typing import Any
 
 from fontTools.misc.psCharStrings import SimpleT2Decompiler
 from fontTools.pens.pointPen import GuessSmoothPointPen
@@ -6,7 +7,14 @@
 
 from fontra.core.protocols import ReadableFontBackend
 
-from ..core.classes import GlobalAxis, Layer, Source, StaticGlyph, VariableGlyph
+from ..core.classes import (
+    GlobalAxis,
+    GlobalDiscreteAxis,
+    Layer,
+    Source,
+    StaticGlyph,
+    VariableGlyph,
+)
 from ..core.path import PackedPath, PackedPathPointPen
 
 
@@ -39,7 +47,7 @@ def __init__(self, *, path):
     def close(self):
         self.font.close()
 
-    async def getGlyphMap(self):
+    async def getGlyphMap(self) -> dict[str, list[int]]:
         return self.glyphMap
 
     async def getGlyph(self, glyphName: str) -> VariableGlyph | None:
@@ -100,13 +108,13 @@ def _getGlyphVariationLocations(self, glyphName):
             }
         return [dict(loc) for loc in sorted(locations)]
 
-    async def getGlobalAxes(self):
+    async def getGlobalAxes(self) -> list[GlobalAxis | GlobalDiscreteAxis]:
         return self.globalAxes
 
-    async def getUnitsPerEm(self):
+    async def getUnitsPerEm(self) -> int:
         return self.font["head"].unitsPerEm
 
-    async def getCustomData(self):
+    async def getCustomData(self) -> dict[str, Any]:
         return {}