diff --git a/src/mares_common.c b/src/mares_common.c
index b1dd944..bac990d 100644
--- a/src/mares_common.c
+++ b/src/mares_common.c
@@ -39,32 +39,11 @@ mares_common_device_init (mares_common_device_t *device, const device_backend_t
 	device_init (&device->base, backend);
 
 	// Set the default values.
-	memset (device->fingerprint, 0, sizeof (device->fingerprint));
-	device->layout = NULL;
 }
 
 
 device_status_t
-mares_common_device_set_fingerprint (device_t *abstract, const unsigned char data[], unsigned int size)
-{
-	mares_common_device_t *device = (mares_common_device_t *) abstract;
-
-	assert (device != NULL);
-
-	if (size && size != sizeof (device->fingerprint))
-		return DEVICE_STATUS_ERROR;
-
-	if (size)
-		memcpy (device->fingerprint, data, sizeof (device->fingerprint));
-	else
-		memset (device->fingerprint, 0, sizeof (device->fingerprint));
-
-	return DEVICE_STATUS_SUCCESS;
-}
-
-
-device_status_t
-mares_common_extract_dives (mares_common_device_t *device, const mares_common_layout_t *layout, const unsigned char data[], dive_callback_t callback, void *userdata)
+mares_common_extract_dives (const mares_common_layout_t *layout, const unsigned char fingerprint[], const unsigned char data[], dive_callback_t callback, void *userdata)
 {
 	assert (layout != NULL);
 
@@ -205,12 +184,12 @@ mares_common_extract_dives (mares_common_device_t *device, const mares_common_la
 		}
 
 		unsigned int fp_offset = offset + length - extra - FP_OFFSET;
-		if (device && memcmp (buffer + fp_offset, device->fingerprint, sizeof (device->fingerprint)) == 0) {
+		if (fingerprint && memcmp (buffer + fp_offset, fingerprint, FP_SIZE) == 0) {
 			free (buffer);
 			return DEVICE_STATUS_SUCCESS;
 		}
 
-		if (callback && !callback (buffer + offset, nbytes, buffer + fp_offset, sizeof (device->fingerprint), userdata)) {
+		if (callback && !callback (buffer + offset, nbytes, buffer + fp_offset, FP_SIZE, userdata)) {
 			free (buffer);
 			return DEVICE_STATUS_SUCCESS;
 		}
diff --git a/src/mares_common.h b/src/mares_common.h
index 0c0e3c6..d928dfb 100644
--- a/src/mares_common.h
+++ b/src/mares_common.h
@@ -38,18 +38,13 @@ typedef struct mares_common_layout_t {
 
 typedef struct mares_common_device_t {
 	device_t base;
-	unsigned char fingerprint[5];
-	const mares_common_layout_t *layout;
 } mares_common_device_t;
 
 void
 mares_common_device_init (mares_common_device_t *device, const device_backend_t *backend);
 
 device_status_t
-mares_common_device_set_fingerprint (device_t *device, const unsigned char data[], unsigned int size);
-
-device_status_t
-mares_common_extract_dives (mares_common_device_t *device, const mares_common_layout_t *layout, const unsigned char data[], dive_callback_t callback, void *userdata);
+mares_common_extract_dives (const mares_common_layout_t *layout, const unsigned char fingerprint[], const unsigned char data[], dive_callback_t callback, void *userdata);
 
 #ifdef __cplusplus
 }
diff --git a/src/mares_nemo.c b/src/mares_nemo.c
index d1327cf..eb2cbcb 100644
--- a/src/mares_nemo.c
+++ b/src/mares_nemo.c
@@ -21,7 +21,6 @@
 
 #include <string.h> // memcpy, memcmp
 #include <stdlib.h> // malloc, free
-#include <assert.h> // assert
 
 #include "device-private.h"
 #include "mares_common.h"
@@ -44,17 +43,19 @@
 #define NEMOAPNEIST 18
 
 typedef struct mares_nemo_device_t {
-	mares_common_device_t base;
+	device_t base;
 	serial_t *port;
+	unsigned char fingerprint[5];
 } mares_nemo_device_t;
 
+static device_status_t mares_nemo_device_set_fingerprint (device_t *abstract, const unsigned char data[], unsigned int size);
 static device_status_t mares_nemo_device_dump (device_t *abstract, dc_buffer_t *buffer);
 static device_status_t mares_nemo_device_foreach (device_t *abstract, dive_callback_t callback, void *userdata);
 static device_status_t mares_nemo_device_close (device_t *abstract);
 
 static const device_backend_t mares_nemo_device_backend = {
 	DEVICE_TYPE_MARES_NEMO,
-	mares_common_device_set_fingerprint, /* set_fingerprint */
+	mares_nemo_device_set_fingerprint, /* set_fingerprint */
 	NULL, /* version */
 	NULL, /* read */
 	NULL, /* write */
@@ -103,10 +104,11 @@ mares_nemo_device_open (device_t **out, const char* name)
 	}
 
 	// Initialize the base class.
-	mares_common_device_init (&device->base, &mares_nemo_device_backend);
+	device_init (&device->base, &mares_nemo_device_backend);
 
 	// Set the default values.
 	device->port = NULL;
+	memset (device->fingerprint, 0, sizeof (device->fingerprint));
 
 	// Open the device.
 	int rc = serial_open (&device->port, name);
@@ -173,12 +175,26 @@ mares_nemo_device_close (device_t *abstract)
 
 
 static device_status_t
-mares_nemo_device_dump (device_t *abstract, dc_buffer_t *buffer)
+mares_nemo_device_set_fingerprint (device_t *abstract, const unsigned char data[], unsigned int size)
 {
 	mares_nemo_device_t *device = (mares_nemo_device_t *) abstract;
 
-	assert (device != NULL);
-	assert (device->base.layout == NULL);
+	if (size && size != sizeof (device->fingerprint))
+		return DEVICE_STATUS_ERROR;
+
+	if (size)
+		memcpy (device->fingerprint, data, sizeof (device->fingerprint));
+	else
+		memset (device->fingerprint, 0, sizeof (device->fingerprint));
+
+	return DEVICE_STATUS_SUCCESS;
+}
+
+
+static device_status_t
+mares_nemo_device_dump (device_t *abstract, dc_buffer_t *buffer)
+{
+	mares_nemo_device_t *device = (mares_nemo_device_t *) abstract;
 
 	// Erase the current contents of the buffer and
 	// pre-allocate the required amount of memory.
@@ -269,11 +285,6 @@ mares_nemo_device_dump (device_t *abstract, dc_buffer_t *buffer)
 static device_status_t
 mares_nemo_device_foreach (device_t *abstract, dive_callback_t callback, void *userdata)
 {
-	mares_common_device_t *device = (mares_common_device_t *) abstract;
-
-	assert (device != NULL);
-	assert (device->layout == NULL);
-
 	dc_buffer_t *buffer = dc_buffer_new (MEMORYSIZE);
 	if (buffer == NULL)
 		return DEVICE_STATUS_MEMORY;
@@ -303,7 +314,7 @@ mares_nemo_device_foreach (device_t *abstract, dive_callback_t callback, void *u
 device_status_t
 mares_nemo_extract_dives (device_t *abstract, const unsigned char data[], unsigned int size, dive_callback_t callback, void *userdata)
 {
-	mares_common_device_t *device = (mares_common_device_t*) abstract;
+	mares_nemo_device_t *device = (mares_nemo_device_t*) abstract;
 
 	if (abstract && !device_is_mares_nemo (abstract))
 		return DEVICE_STATUS_TYPE_MISMATCH;
@@ -311,6 +322,8 @@ mares_nemo_extract_dives (device_t *abstract, const unsigned char data[], unsign
 	if (size < PACKETSIZE)
 		return DEVICE_STATUS_ERROR;
 
+	unsigned char *fingerprint = (device ? device->fingerprint : NULL);
+
 	const mares_common_layout_t *layout = NULL;
 	switch (data[1]) {
 	case NEMO:
@@ -328,5 +341,5 @@ mares_nemo_extract_dives (device_t *abstract, const unsigned char data[], unsign
 	if (size < layout->memsize)
 		return DEVICE_STATUS_ERROR;
 
-	return mares_common_extract_dives (device, layout, data, callback, userdata);
+	return mares_common_extract_dives (layout, fingerprint, data, callback, userdata);
 }
diff --git a/src/mares_puck.c b/src/mares_puck.c
index e5436fd..3c158b0 100644
--- a/src/mares_puck.c
+++ b/src/mares_puck.c
@@ -47,8 +47,11 @@
 typedef struct mares_puck_device_t {
 	mares_common_device_t base;
 	serial_t *port;
+	const mares_common_layout_t *layout;
+	unsigned char fingerprint[5];
 } mares_puck_device_t;
 
+static device_status_t mares_puck_device_set_fingerprint (device_t *abstract, const unsigned char data[], unsigned int size);
 static device_status_t mares_puck_device_read (device_t *abstract, unsigned int address, unsigned char data[], unsigned int size);
 static device_status_t mares_puck_device_dump (device_t *abstract, dc_buffer_t *buffer);
 static device_status_t mares_puck_device_foreach (device_t *abstract, dive_callback_t callback, void *userdata);
@@ -56,7 +59,7 @@ static device_status_t mares_puck_device_close (device_t *abstract);
 
 static const device_backend_t mares_puck_device_backend = {
 	DEVICE_TYPE_MARES_PUCK,
-	mares_common_device_set_fingerprint, /* set_fingerprint */
+	mares_puck_device_set_fingerprint, /* set_fingerprint */
 	NULL, /* version */
 	mares_puck_device_read, /* read */
 	NULL, /* write */
@@ -117,6 +120,8 @@ mares_puck_device_open (device_t **out, const char* name)
 
 	// Set the default values.
 	device->port = NULL;
+	device->layout = NULL;
+	memset (device->fingerprint, 0, sizeof (device->fingerprint));
 
 	// Open the device.
 	int rc = serial_open (&device->port, name);
@@ -167,17 +172,17 @@ mares_puck_device_open (device_t **out, const char* name)
 	// Override the base class values.
 	switch (header[1]) {
 	case NEMOWIDE:
-		device->base.layout = &mares_nemowide_layout;
+		device->layout = &mares_nemowide_layout;
 		break;
 	case NEMOAIR:
 	case PUCKAIR:
-		device->base.layout = &mares_nemoair_layout;
+		device->layout = &mares_nemoair_layout;
 		break;
 	case PUCK:
-		device->base.layout = &mares_puck_layout;
+		device->layout = &mares_puck_layout;
 		break;
 	default: // Unknown, try puck
-		device->base.layout = &mares_puck_layout;
+		device->layout = &mares_puck_layout;
 		break;
 	}
 
@@ -208,6 +213,23 @@ mares_puck_device_close (device_t *abstract)
 }
 
 
+static device_status_t
+mares_puck_device_set_fingerprint (device_t *abstract, const unsigned char data[], unsigned int size)
+{
+	mares_puck_device_t *device = (mares_puck_device_t *) abstract;
+
+	if (size && size != sizeof (device->fingerprint))
+		return DEVICE_STATUS_ERROR;
+
+	if (size)
+		memcpy (device->fingerprint, data, sizeof (device->fingerprint));
+	else
+		memset (device->fingerprint, 0, sizeof (device->fingerprint));
+
+	return DEVICE_STATUS_SUCCESS;
+}
+
+
 static void
 mares_puck_convert_binary_to_ascii (const unsigned char input[], unsigned int isize, unsigned char output[], unsigned int osize)
 {
@@ -386,7 +408,7 @@ mares_puck_device_read (device_t *abstract, unsigned int address, unsigned char
 static device_status_t
 mares_puck_device_dump (device_t *abstract, dc_buffer_t *buffer)
 {
-	mares_common_device_t *device = (mares_common_device_t *) abstract;
+	mares_puck_device_t *device = (mares_puck_device_t *) abstract;
 
 	assert (device != NULL);
 	assert (device->layout != NULL);
@@ -406,7 +428,7 @@ mares_puck_device_dump (device_t *abstract, dc_buffer_t *buffer)
 static device_status_t
 mares_puck_device_foreach (device_t *abstract, dive_callback_t callback, void *userdata)
 {
-	mares_common_device_t *device = (mares_common_device_t *) abstract;
+	mares_puck_device_t *device = (mares_puck_device_t *) abstract;
 
 	assert (device != NULL);
 	assert (device->layout != NULL);
@@ -429,7 +451,7 @@ mares_puck_device_foreach (device_t *abstract, dive_callback_t callback, void *u
 	devinfo.serial = array_uint16_be (data + 8);
 	device_event_emit (abstract, DEVICE_EVENT_DEVINFO, &devinfo);
 
-	rc = mares_common_extract_dives (device, device->layout, data, callback, userdata);
+	rc = mares_common_extract_dives (device->layout, device->fingerprint, data, callback, userdata);
 
 	dc_buffer_free (buffer);
 
@@ -440,7 +462,7 @@ mares_puck_device_foreach (device_t *abstract, dive_callback_t callback, void *u
 device_status_t
 mares_puck_extract_dives (device_t *abstract, const unsigned char data[], unsigned int size, dive_callback_t callback, void *userdata)
 {
-	mares_common_device_t *device = (mares_common_device_t*) abstract;
+	mares_puck_device_t *device = (mares_puck_device_t*) abstract;
 
 	if (abstract && !device_is_mares_puck (abstract))
 		return DEVICE_STATUS_TYPE_MISMATCH;
@@ -448,6 +470,8 @@ mares_puck_extract_dives (device_t *abstract, const unsigned char data[], unsign
 	if (size < PACKETSIZE)
 		return DEVICE_STATUS_ERROR;
 
+	unsigned char *fingerprint = (device ? device->fingerprint : NULL);
+
 	const mares_common_layout_t *layout = NULL;
 	switch (data[1]) {
 	case NEMOWIDE:
@@ -468,5 +492,5 @@ mares_puck_extract_dives (device_t *abstract, const unsigned char data[], unsign
 	if (size < layout->memsize)
 		return DEVICE_STATUS_ERROR;
 
-	return mares_common_extract_dives (device, layout, data, callback, userdata);
+	return mares_common_extract_dives (layout, fingerprint, data, callback, userdata);
 }