diff --git a/configure.in b/configure.in
index 21290d3..fdc0870 100644
--- a/configure.in
+++ b/configure.in
@@ -8,6 +8,8 @@ AC_PROG_CC
 AM_PROG_LIBTOOL
 AC_PROG_INSTALL
 
+AC_CHECK_SIZEOF(void *, 8)
+
 # set the libtool so version numbers
 lt_major=4
 lt_revision=0
diff --git a/src/fcp.c b/src/fcp.c
index 9bc7fa1..5c29a6e 100644
--- a/src/fcp.c
+++ b/src/fcp.c
@@ -27,8 +27,8 @@ static int do_fcp_listen(struct raw1394_handle *handle, int startstop)
         req->type = RAW1394_REQ_FCP_LISTEN;
         req->generation = handle->generation;
         req->misc = startstop;
-        req->tag = (__u64)&rh;
-        req->recvb = (__u64)handle->buffer;
+        req->tag = ptr2int(&rh);
+        req->recvb = ptr2int(handle->buffer);
         req->length = 512;
 
         err = write(handle->fd, req, sizeof(*req));
diff --git a/src/iso.c b/src/iso.c
index 7df6ec0..8d69b57 100644
--- a/src/iso.c
+++ b/src/iso.c
@@ -28,8 +28,8 @@ static int do_iso_listen(struct raw1394_handle *handle, int channel)
         req->type = RAW1394_REQ_ISO_LISTEN;
         req->generation = handle->generation;
         req->misc = channel;
-        req->tag = (__u64)&rh;
-        req->recvb = (__u64)handle->buffer;
+        req->tag = ptr2int(&rh);
+        req->recvb = ptr2int(handle->buffer);
         req->length = HBUF_SIZE;
 
         err = write(handle->fd, req, sizeof(*req));
diff --git a/src/main.c b/src/main.c
index 0fe887b..744543c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -158,7 +158,7 @@ int raw1394_get_port_info(struct raw1394_handle *handle,
         CLEAR_REQ(req);
         req->type = RAW1394_REQ_LIST_CARDS;
         req->generation = handle->generation;
-        req->recvb = (__u64)handle->buffer;
+        req->recvb = ptr2int(handle->buffer);
         req->length = HBUF_SIZE;
 
         while (1) {
diff --git a/src/raw1394_private.h b/src/raw1394_private.h
index 86688c7..616ac75 100644
--- a/src/raw1394_private.h
+++ b/src/raw1394_private.h
@@ -32,4 +32,12 @@ int _raw1394_sync_cb(struct raw1394_handle*, struct sync_cb_data*, int);
 #define HBUF_SIZE 8192
 #define CLEAR_REQ(reqp) memset((reqp), 0, sizeof(struct raw1394_request))
 
+#if SIZEOF_VOID_P == 4
+#define int2ptr(x) ((void *)(__u32)x)
+#define ptr2int(x) ((__u64)(__u32)x)
+#else
+#define int2ptr(x) ((void *)x)
+#define ptr2int(x) ((__u64)x)
+#endif
+
 #endif /* _RAW1394_PRIVATE_H */
diff --git a/src/readwrite.c b/src/readwrite.c
index 1e12b6c..333db8a 100644
--- a/src/readwrite.c
+++ b/src/readwrite.c
@@ -31,7 +31,7 @@ int raw1394_start_read(struct raw1394_handle *handle, nodeid_t node,
 
         req->address = ((__u64)node << 48) | addr;
         req->length = length;
-        req->recvb = (__u64)buffer;
+        req->recvb = ptr2int(buffer);
 
         return (int)write(handle->fd, req, sizeof(*req));
 }
@@ -50,7 +50,7 @@ int raw1394_start_write(struct raw1394_handle *handle, nodeid_t node,
 
         req->address = ((__u64)node << 48) | addr;
         req->length = length;
-        req->sendb = (__u64)data;
+        req->sendb = ptr2int(data);
 
         return (int)write(handle->fd, req, sizeof(*req));
 }
@@ -74,8 +74,8 @@ int raw1394_start_lock(struct raw1394_handle *handle, nodeid_t node,
         req->tag = tag;
 
         req->address = ((__u64)node << 48) | addr;
-        req->sendb = (__u64)sendbuf;
-        req->recvb = (__u64)result;
+        req->sendb = ptr2int(sendbuf);
+        req->recvb = ptr2int(result);
         req->misc = extcode;
 
         switch (extcode) {
@@ -110,7 +110,7 @@ int raw1394_start_iso_write(struct raw1394_handle *handle, unsigned int channel,
         req->address = ((__u64)channel << 48) | speed;
         req->misc = (tag << 16) | sy;
         req->length = length;
-        req->sendb = data;
+        req->sendb = ptr2int(data);
 
         return (int)write(handle->fd, req, sizeof(*req));
 }