diff --git a/pkgs/applications/science/math/calc/default.nix b/pkgs/applications/science/math/calc/default.nix
index 4cfc4fb182b8..86ec445d9b3e 100644
--- a/pkgs/applications/science/math/calc/default.nix
+++ b/pkgs/applications/science/math/calc/default.nix
@@ -21,7 +21,7 @@ stdenv.mkDerivation (finalAttrs: {
   };
 
   postPatch = ''
-    substituteInPlace Makefile \
+    substituteInPlace Makefile.target \
       --replace '-install_name ''${LIBDIR}/libcalc''${LIB_EXT_VERSION}' '-install_name ''${T}''${LIBDIR}/libcalc''${LIB_EXT_VERSION}' \
       --replace '-install_name ''${LIBDIR}/libcustcalc''${LIB_EXT_VERSION}' '-install_name ''${T}''${LIBDIR}/libcustcalc''${LIB_EXT_VERSION}'
   '';