diff --git a/lib/internal.h b/lib/internal.h
index 605c470..b506233 100644
--- a/lib/internal.h
+++ b/lib/internal.h
@@ -47,6 +47,20 @@ struct ykpiv_state {
 	int verbose;
 };
 
+union u_APDU {
+  struct {
+    unsigned char cla;
+    unsigned char ins;
+    unsigned char p1;
+    unsigned char p2;
+    unsigned char lc;
+    unsigned char data[0xff];
+  } st;
+  unsigned char raw[0xff + 5];
+};
+
+typedef union u_APDU APDU;
+
 unsigned const char aid[] = {
 	0xa0, 0x00, 0x00, 0x03, 0x08
 };
diff --git a/lib/ykpiv.c b/lib/ykpiv.c
index de2a434..a6f5572 100644
--- a/lib/ykpiv.c
+++ b/lib/ykpiv.c
@@ -38,20 +38,6 @@
 #include "internal.h"
 #include "ykpiv.h"
 
-union u_APDU {
-  struct {
-    unsigned char cla;
-    unsigned char ins;
-    unsigned char p1;
-    unsigned char p2;
-    unsigned char lc;
-    unsigned char data[0xff];
-  } st;
-  unsigned char raw[0xff + 5];
-};
-
-typedef union u_APDU APDU;
-
 static void dump_hex(const unsigned char *buf, unsigned int len) {
   unsigned int i;
   for (i = 0; i < len; i++) {