diff --git a/src/mantine-core/src/Modal/Modal.styles.ts b/src/mantine-core/src/Modal/Modal.styles.ts
index 955f8936e68..2ef6c55defa 100644
--- a/src/mantine-core/src/Modal/Modal.styles.ts
+++ b/src/mantine-core/src/Modal/Modal.styles.ts
@@ -71,7 +71,7 @@ export default createStyles(
 
     modal: {
       position: 'relative',
-      width: fullScreen ? undefined : theme.fn.size({ sizes, size }),
+      width: fullScreen ? '100vw' : theme.fn.size({ sizes, size }),
       borderRadius: fullScreen ? 0 : undefined,
       outline: 0,
       backgroundColor: theme.colorScheme === 'dark' ? theme.colors.dark[7] : theme.white,