diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 0.6.1.1
+
+* Added `HasCallStack` to partial functions.
+
 # 0.6.1
 
 * Added `instance FromBuilder ByteString` (for both lazy and strict
diff --git a/fmt.cabal b/fmt.cabal
--- a/fmt.cabal
+++ b/fmt.cabal
@@ -1,5 +1,5 @@
 name:                fmt
-version:             0.6.1
+version:             0.6.1.1
 synopsis:            A new formatting library
 description:
   A new formatting library that tries to be simple to understand while still
@@ -46,7 +46,7 @@
 maintainer:          yom@artyom.me
 -- copyright:
 category:            Text
-tested-with:         GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.1
+tested-with:         GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.2
 build-type:          Simple
 extra-source-files:  CHANGELOG.md
                      tests/doctest-config.json
@@ -70,6 +70,7 @@
   build-depends:       base >=4.6 && <5,
                        base64-bytestring,
                        bytestring,
+                       call-stack,
                        containers,
                        formatting >= 6.3.4,
                        microlens >= 0.3,
diff --git a/lib/Fmt/Internal/Numeric.hs b/lib/Fmt/Internal/Numeric.hs
--- a/lib/Fmt/Internal/Numeric.hs
+++ b/lib/Fmt/Internal/Numeric.hs
@@ -1,10 +1,12 @@
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE CPP #-}
 
 
 module Fmt.Internal.Numeric where
 
 
+import           Data.CallStack
 #if __GLASGOW_HASKELL__ < 804
 import           Data.Monoid ((<>))
 #endif
@@ -51,7 +53,7 @@
 >>> baseF 36 10000
 "7ps"
 -}
-baseF :: Integral a => Int -> a -> Builder
+baseF :: (HasCallStack, Integral a) => Int -> a -> Builder
 baseF numBase = build . atBase numBase
 
 ----------------------------------------------------------------------------
diff --git a/lib/Fmt/Internal/Template.hs b/lib/Fmt/Internal/Template.hs
--- a/lib/Fmt/Internal/Template.hs
+++ b/lib/Fmt/Internal/Template.hs
@@ -2,6 +2,7 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE UndecidableInstances #-}
 
 
@@ -9,6 +10,7 @@
 module Fmt.Internal.Template where
 
 
+import Data.CallStack
 import Data.String (IsString(..))
 import Data.Text (Text, splitOn)
 import Data.Text.Lazy.Builder hiding (fromString)
@@ -35,13 +37,13 @@
 >>> format "0x{} + 0x{} = 0x{}" (hexF 130) (hexF 270) (hexF (130+270))
 0x82 + 0x10e = 0x190
 -}
-format :: FormatType r => Format -> r
+format :: (HasCallStack, FormatType r) => Format -> r
 format f = format' f []
 {-# INLINE format #-}
 
 {- | Like 'format', but adds a newline.
 -}
-formatLn :: FormatType r => Format -> r
+formatLn :: (HasCallStack, FormatType r) => Format -> r
 formatLn f = format' (f <> "\n") []
 {-# INLINE formatLn #-}