diff --git a/src/os/windows/font_win32.cpp b/src/os/windows/font_win32.cpp
--- a/src/os/windows/font_win32.cpp
+++ b/src/os/windows/font_win32.cpp
@@ -476,9 +476,10 @@ void Win32FontCache::ClearFontCache()
 		GetGlyphOutline(this->dc, key, GGO_GLYPH_INDEX | (aa ? GGO_GRAY8_BITMAP : GGO_BITMAP), &gm, size, bmp, &mat);
 	}
 
-	/* Add 1 pixel for the shadow on the medium font. Our sprite must be at least 1x1 pixel. */
-	uint width = std::max(1U, (uint)gm.gmBlackBoxX + (this->fs == FS_NORMAL));
-	uint height = std::max(1U, (uint)gm.gmBlackBoxY + (this->fs == FS_NORMAL));
+	/* Add 1 scaled pixel for the shadow on the medium font. Our sprite must be at least 1x1 pixel. */
+	uint shadow = (this->fs == FS_NORMAL) ? ScaleGUITrad(1) : 0;
+	uint width = std::max(1U, (uint)gm.gmBlackBoxX + shadow);
+	uint height = std::max(1U, (uint)gm.gmBlackBoxY + shadow);
 
 	/* Limit glyph size to prevent overflows later on. */
 	if (width > MAX_GLYPH_DIM || height > MAX_GLYPH_DIM) usererror("Font glyph is too large");
@@ -506,8 +507,8 @@ void Win32FontCache::ClearFontCache()
 			for (uint y = 0; y < gm.gmBlackBoxY; y++) {
 				for (uint x = 0; x < gm.gmBlackBoxX; x++) {
 					if (aa ? (bmp[x + y * pitch] > 0) : HasBit(bmp[(x / 8) + y * pitch], 7 - (x % 8))) {
-						sprite.data[1 + x + (1 + y) * sprite.width].m = SHADOW_COLOUR;
-						sprite.data[1 + x + (1 + y) * sprite.width].a = aa ? (bmp[x + y * pitch] << 2) - 1 : 0xFF;
+						sprite.data[shadow + x + (shadow + y) * sprite.width].m = SHADOW_COLOUR;
+						sprite.data[shadow + x + (shadow + y) * sprite.width].a = aa ? (bmp[x + y * pitch] << 2) - 1 : 0xFF;
 					}
 				}
 			}