diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Revision history for yasi
 
+## 0.1.2.1 -- 2021-03-15
+
+ * Allow to interpolate lazy into strict `ByteString`s and vice versa.
+
 ## 0.1.2.0 -- 2021-03-15
 
  * Add `unindent` utility function.
diff --git a/src/Yasi/Internal.hs b/src/Yasi/Internal.hs
--- a/src/Yasi/Internal.hs
+++ b/src/Yasi/Internal.hs
@@ -156,5 +156,11 @@
 instance Stringy B.ByteString B.ByteString where
   stringy = id
 
+instance Stringy B.ByteString BL.ByteString where
+  stringy = BL.fromStrict
+
 instance Stringy BL.ByteString BL.ByteString where
   stringy = id
+
+instance Stringy BL.ByteString B.ByteString where
+  stringy = BL.toStrict
diff --git a/yasi.cabal b/yasi.cabal
--- a/yasi.cabal
+++ b/yasi.cabal
@@ -1,6 +1,6 @@
 cabal-version: 2.4
 name: yasi
-version: 0.1.2.0
+version: 0.1.2.1
 
 synopsis: Yet another string interpolator
 description: