diff --git a/lib/python/qmk/painter_qff.py b/lib/python/qmk/painter_qff.py
index 746bb166e52..f7f8a264930 100644
--- a/lib/python/qmk/painter_qff.py
+++ b/lib/python/qmk/painter_qff.py
@@ -22,6 +22,11 @@ def o24(i):
 
 
 class QFFGlyphInfo(AttrDict):
+    GLYPH_WIDTH_BITS = 6
+    GLYPH_WIDTH_MASK = (1 << GLYPH_WIDTH_BITS) - 1
+    GLYPH_OFFSET_BITS = 18
+    GLYPH_OFFSET_MASK = ((1 << GLYPH_OFFSET_BITS) - 1) << GLYPH_WIDTH_BITS
+
     def __init__(self, *args, **kwargs):
         super().__init__()
 
@@ -35,7 +40,7 @@ class QFFGlyphInfo(AttrDict):
         if include_code_point is True:
             fp.write(o24(ord(self.code_point)))
 
-        value = ((self.data_offset << 6) & 0xFFFFC0) | (self.w & 0x3F)
+        value = ((self.data_offset << self.GLYPH_WIDTH_BITS) & self.GLYPH_OFFSET_MASK) | (self.w & self.GLYPH_WIDTH_MASK)
         fp.write(o24(value))
 
 
@@ -228,8 +233,17 @@ class QFFFont:
         last_offset = 0
         for x in range(1, width):
             if pixels[x, 0] == glyph_split_color:
+                if x > ((1 << QFFGlyphInfo.GLYPH_OFFSET_BITS) - 1):
+                    self.logger.error("A glyph has too big of an offset for QFF's encoding")
+                    exit(1)
                 glyph_pixel_offsets.append(x)
-                glyph_pixel_widths.append(x - last_offset)
+
+                width = x - last_offset
+                if width > QFFGlyphInfo.GLYPH_WIDTH_MASK:
+                    self.logger.error("A glyph is too wide for QFF's encoding")
+                    exit(1)
+                glyph_pixel_widths.append(width)
+
                 last_offset = x
         glyph_pixel_widths.append(width - last_offset)