diff --git a/src/Mima/Asm/Phase1.hs b/src/Mima/Asm/Phase1.hs
index 149bc66..877f818 100644
--- a/src/Mima/Asm/Phase1.hs
+++ b/src/Mima/Asm/Phase1.hs
@@ -353,7 +353,7 @@ asmToken
     fmap (uncurry TokenComment) (withSpan comment)
 
 parsePhase1 :: Parser Phase1
-parsePhase1 = many (space *> asmToken)
+parsePhase1 = many (space *> asmToken) <* eof
 
 -- | A small helper for visualizing the parse.
 --