diff --git a/src/Mima/Instruction.hs b/src/Mima/Instruction.hs
index f85d175..bd03210 100644
--- a/src/Mima/Instruction.hs
+++ b/src/Mima/Instruction.hs
@@ -7,7 +7,7 @@ module Mima.Instruction
   , wordToInstruction
   ) where
 
-import qualified Data.Map as Map
+import qualified Data.Map.Strict as Map
 import qualified Data.Text as T
 import           Data.Word
 
diff --git a/src/Mima/State.hs b/src/Mima/State.hs
index 916c93b..bf34fcf 100644
--- a/src/Mima/State.hs
+++ b/src/Mima/State.hs
@@ -17,7 +17,7 @@ module Mima.State
   ) where
 
 import           Data.Bits
-import qualified Data.Map as Map
+import qualified Data.Map.Strict as Map
 import           Data.Maybe
 import qualified Data.Text as T