diff --git a/gencat/pdf.c b/gencat/pdf.c
index a45d1c8..f966bfb 100644
--- a/gencat/pdf.c
+++ b/gencat/pdf.c
@@ -9,6 +9,7 @@
  * (at your option) any later version.
  */
 
+#define _GNU_SOURCE /* for strcasecmp */
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -121,7 +122,7 @@ static int comp(const void *a, const void *b)
 	const struct index *ai = a;
 	const struct index *bi = b;
 
-	return strcmp(ai->s, bi->s);
+	return strcasecmp(ai->s, bi->s);
 }