diff --git a/configure.ac b/configure.ac
index 9fd8d35c..b2b63958 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,6 +41,7 @@ m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
 # Checks for programs.
 AC_PROG_CC
+AC_PROG_CC_C99
 AM_PROG_CC_C_O
 
 # Initialize libtool