diff --git a/configure.ac b/configure.ac
index 8e30906..ea81cae 100644
--- a/configure.ac
+++ b/configure.ac
@@ -77,7 +77,7 @@ if test "x$DO_IRRKLANG" = "xyes"; then
 else
   AC_MSG_RESULT($DO_IRRKLANG)
   IRRKLANG_DIR=
-  IRRKLANG_LIB=$(prefix)/bin/libIrrKlang.so
+  IRRKLANG_LIB=${prefix}/bin/libIrrKlang.so
 fi
 AC_SUBST([IRRKLANG_DIR])
 AC_SUBST([IRRKLANG_LIB])