diff --git a/configure.ac b/configure.ac
index 515e727..d5ccebc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@ dnl Checks for header files.
 AC_HEADER_STDC
 
 dnl Checks for libraries.
-PKG_CHECK_MODULES(IDPC, libxml-2.0 neon lasso >= 0.4.1 openssl)
+PKG_CHECK_MODULES(IDPC, libxml-2.0 neon lasso = 0.4.1 openssl)
 AC_SUBST(IDPC_CFLAGS)
 AC_SUBST(IDPC_LIBS)