diff --git a/channels/printer/client/cups/printer_cups.c b/channels/printer/client/cups/printer_cups.c
index 6e65f6560..8c4a41ee3 100644
--- a/channels/printer/client/cups/printer_cups.c
+++ b/channels/printer/client/cups/printer_cups.c
@@ -20,6 +20,8 @@
  * limitations under the License.
  */
 
+#include <winpr/assert.h>
+
 #include <freerdp/config.h>
 
 #include <stdio.h>
@@ -50,7 +52,7 @@ typedef struct
 {
 	rdpPrintJob printjob;
 
-	void* printjob_object;
+	http_t* printjob_object;
 	int printjob_id;
 } rdpCupsPrintJob;
 
@@ -63,12 +65,13 @@ typedef struct
 
 static void printer_cups_get_printjob_name(char* buf, size_t size, size_t id)
 {
-	time_t tt;
 	struct tm tres;
-	struct tm* t;
+	const time_t tt = time(NULL);
+	const struct tm* t = localtime_r(&tt, &tres);
+
+	WINPR_ASSERT(buf);
+	WINPR_ASSERT(size > 0);
 
-	tt = time(NULL);
-	t = localtime_r(&tt, &tres);
 	sprintf_s(buf, size - 1, "FreeRDP Print %04d-%02d-%02d %02d-%02d-%02d - Job %" PRIdz,
 	          t->tm_year + 1900, t->tm_mon + 1, t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec, id);
 }
@@ -82,6 +85,8 @@ static UINT printer_cups_write_printjob(rdpPrintJob* printjob, const BYTE* data,
 {
 	rdpCupsPrintJob* cups_printjob = (rdpCupsPrintJob*)printjob;
 
+	WINPR_ASSERT(cups_printjob);
+
 #ifndef _CUPS_API_1_4
 
 	{
@@ -104,7 +109,7 @@ static UINT printer_cups_write_printjob(rdpPrintJob* printjob, const BYTE* data,
 
 #else
 
-	cupsWriteRequestData((http_t*)cups_printjob->printjob_object, (const char*)data, size);
+	cupsWriteRequestData(cups_printjob->printjob_object, (const char*)data, size);
 
 #endif
 
@@ -114,6 +119,9 @@ static UINT printer_cups_write_printjob(rdpPrintJob* printjob, const BYTE* data,
 static void printer_cups_close_printjob(rdpPrintJob* printjob)
 {
 	rdpCupsPrintJob* cups_printjob = (rdpCupsPrintJob*)printjob;
+	rdpCupsPrinter* cups_printer;
+
+	WINPR_ASSERT(cups_printjob);
 
 #ifndef _CUPS_API_1_4
 
@@ -133,13 +141,16 @@ static void printer_cups_close_printjob(rdpPrintJob* printjob)
 
 #else
 
-	cupsFinishDocument((http_t*)cups_printjob->printjob_object, printjob->printer->name);
+	cupsFinishDocument(cups_printjob->printjob_object, printjob->printer->name);
 	cups_printjob->printjob_id = 0;
-	httpClose((http_t*)cups_printjob->printjob_object);
+	httpClose(cups_printjob->printjob_object);
 
 #endif
 
-	((rdpCupsPrinter*)printjob->printer)->printjob = NULL;
+	cups_printer = (rdpCupsPrinter*)printjob->printer;
+	WINPR_ASSERT(cups_printer);
+
+	cups_printer->printjob = NULL;
 	free(cups_printjob);
 }
 
@@ -148,6 +159,8 @@ static rdpPrintJob* printer_cups_create_printjob(rdpPrinter* printer, UINT32 id)
 	rdpCupsPrinter* cups_printer = (rdpCupsPrinter*)printer;
 	rdpCupsPrintJob* cups_printjob;
 
+	WINPR_ASSERT(cups_printer);
+
 	if (cups_printer->printjob != NULL)
 		return NULL;
 
@@ -190,47 +203,57 @@ static rdpPrintJob* printer_cups_create_printjob(rdpPrinter* printer, UINT32 id)
 		printer_cups_get_printjob_name(buf, sizeof(buf), cups_printjob->printjob.id);
 
 		cups_printjob->printjob_id =
-		    cupsCreateJob((http_t*)cups_printjob->printjob_object, printer->name, buf, 0, NULL);
+		    cupsCreateJob(cups_printjob->printjob_object, printer->name, buf, 0, NULL);
 
 		if (!cups_printjob->printjob_id)
 		{
-			httpClose((http_t*)cups_printjob->printjob_object);
+			httpClose(cups_printjob->printjob_object);
 			free(cups_printjob);
 			return NULL;
 		}
 
-		cupsStartDocument((http_t*)cups_printjob->printjob_object, printer->name,
-		                  cups_printjob->printjob_id, buf, CUPS_FORMAT_AUTO, 1);
+		cupsStartDocument(cups_printjob->printjob_object, printer->name, cups_printjob->printjob_id,
+		                  buf, CUPS_FORMAT_AUTO, 1);
 	}
 
 #endif
 
 	cups_printer->printjob = cups_printjob;
 
-	return (rdpPrintJob*)cups_printjob;
+	return &cups_printjob->printjob;
 }
 
 static rdpPrintJob* printer_cups_find_printjob(rdpPrinter* printer, UINT32 id)
 {
 	rdpCupsPrinter* cups_printer = (rdpCupsPrinter*)printer;
 
+	WINPR_ASSERT(cups_printer);
+
 	if (cups_printer->printjob == NULL)
 		return NULL;
 	if (cups_printer->printjob->printjob.id != id)
 		return NULL;
 
-	return (rdpPrintJob*)cups_printer->printjob;
+	return &cups_printer->printjob->printjob;
 }
 
 static void printer_cups_free_printer(rdpPrinter* printer)
 {
 	rdpCupsPrinter* cups_printer = (rdpCupsPrinter*)printer;
 
+	WINPR_ASSERT(cups_printer);
+
 	if (cups_printer->printjob)
-		cups_printer->printjob->printjob.Close((rdpPrintJob*)cups_printer->printjob);
+	{
+		WINPR_ASSERT(cups_printer->printjob->printjob.Close);
+		cups_printer->printjob->printjob.Close(&cups_printer->printjob->printjob);
+	}
 
 	if (printer->backend)
+	{
+		WINPR_ASSERT(printer->backend->ReleaseRef);
 		printer->backend->ReleaseRef(printer->backend);
+	}
 	free(printer->name);
 	free(printer->driver);
 	free(printer);
@@ -282,8 +305,12 @@ static rdpPrinter* printer_cups_new_printer(rdpCupsPrinterDriver* cups_driver, c
 	cups_printer->printer.AddRef = printer_cups_add_ref_printer;
 	cups_printer->printer.ReleaseRef = printer_cups_release_ref_printer;
 
+	WINPR_ASSERT(cups_printer->printer.AddRef);
 	cups_printer->printer.AddRef(&cups_printer->printer);
+
+	WINPR_ASSERT(cups_printer->printer.backend->AddRef);
 	cups_printer->printer.backend->AddRef(cups_printer->printer.backend);
+
 	return &cups_printer->printer;
 
 fail:
@@ -307,20 +334,19 @@ static void printer_cups_release_enum_printers(rdpPrinter** printers)
 static rdpPrinter** printer_cups_enum_printers(rdpPrinterDriver* driver)
 {
 	rdpPrinter** printers;
-	int num_printers;
-	cups_dest_t* dests;
-	cups_dest_t* dest;
-	int num_dests;
+	int num_printers = 0;
+	cups_dest_t* dests = NULL;
+	cups_dest_t* dest = NULL;
 	int i;
 	BOOL haveDefault = FALSE;
+	const int num_dests = cupsGetDests(&dests);
+
+	WINPR_ASSERT(driver);
 
-	num_dests = cupsGetDests(&dests);
 	printers = (rdpPrinter**)calloc(num_dests + 1, sizeof(rdpPrinter*));
 	if (!printers)
 		return NULL;
 
-	num_printers = 0;
-
 	for (i = 0, dest = dests; i < num_dests; i++, dest++)
 	{
 		if (dest->instance == NULL)
@@ -356,6 +382,7 @@ static rdpPrinter* printer_cups_get_printer(rdpPrinterDriver* driver, const char
 {
 	rdpCupsPrinterDriver* cups_driver = (rdpCupsPrinterDriver*)driver;
 
+	WINPR_ASSERT(cups_driver);
 	return printer_cups_new_printer(cups_driver, name, driverName,
 	                                cups_driver->id_sequence == 1 ? TRUE : FALSE);
 }
@@ -373,6 +400,9 @@ static rdpCupsPrinterDriver* uniq_cups_driver = NULL;
 static void printer_cups_release_ref_driver(rdpPrinterDriver* driver)
 {
 	rdpCupsPrinterDriver* cups_driver = (rdpCupsPrinterDriver*)driver;
+
+	WINPR_ASSERT(cups_driver);
+
 	if (cups_driver->references <= 1)
 	{
 		if (uniq_cups_driver == cups_driver)
@@ -402,6 +432,7 @@ rdpPrinterDriver* cups_freerdp_printer_client_subsystem_entry(void)
 		uniq_cups_driver->id_sequence = 1;
 	}
 
+	WINPR_ASSERT(uniq_cups_driver->driver.AddRef);
 	uniq_cups_driver->driver.AddRef(&uniq_cups_driver->driver);
 
 	return &uniq_cups_driver->driver;
diff --git a/channels/printer/client/printer_main.c b/channels/printer/client/printer_main.c
index 80e89a643..be80766ff 100644
--- a/channels/printer/client/printer_main.c
+++ b/channels/printer/client/printer_main.c
@@ -28,6 +28,7 @@
 #include <string.h>
 
 #include <winpr/crt.h>
+#include <winpr/assert.h>
 #include <winpr/string.h>
 #include <winpr/synch.h>
 #include <winpr/thread.h>
@@ -426,9 +427,15 @@ static UINT printer_process_irp_create(PRINTER_DEVICE* printer_dev, IRP* irp)
 {
 	rdpPrintJob* printjob = NULL;
 
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(irp);
+
 	if (printer_dev->printer)
+	{
+		WINPR_ASSERT(printer_dev->printer->CreatePrintJob);
 		printjob =
 		    printer_dev->printer->CreatePrintJob(printer_dev->printer, irp->devman->id_sequence++);
+	}
 
 	if (printjob)
 	{
@@ -452,8 +459,14 @@ static UINT printer_process_irp_close(PRINTER_DEVICE* printer_dev, IRP* irp)
 {
 	rdpPrintJob* printjob = NULL;
 
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(irp);
+
 	if (printer_dev->printer)
+	{
+		WINPR_ASSERT(printer_dev->printer->FindPrintJob);
 		printjob = printer_dev->printer->FindPrintJob(printer_dev->printer, irp->FileId);
+	}
 
 	if (!printjob)
 	{
@@ -481,6 +494,9 @@ static UINT printer_process_irp_write(PRINTER_DEVICE* printer_dev, IRP* irp)
 	UINT error = CHANNEL_RC_OK;
 	void* ptr;
 
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(irp);
+
 	if (!Stream_CheckAndLogRequiredLength(TAG, irp->input, 32))
 		return ERROR_INVALID_DATA;
 	Stream_Read_UINT32(irp->input, Length);
@@ -490,7 +506,10 @@ static UINT printer_process_irp_write(PRINTER_DEVICE* printer_dev, IRP* irp)
 	if (!Stream_SafeSeek(irp->input, Length))
 		return ERROR_INVALID_DATA;
 	if (printer_dev->printer)
+	{
+		WINPR_ASSERT(printer_dev->printer->FindPrintJob);
 		printjob = printer_dev->printer->FindPrintJob(printer_dev->printer, irp->FileId);
+	}
 
 	if (!printjob)
 	{
@@ -510,6 +529,8 @@ static UINT printer_process_irp_write(PRINTER_DEVICE* printer_dev, IRP* irp)
 
 	Stream_Write_UINT32(irp->output, Length);
 	Stream_Write_UINT8(irp->output, 0); /* Padding */
+
+	WINPR_ASSERT(irp->Complete);
 	return irp->Complete(irp);
 }
 
@@ -520,7 +541,12 @@ static UINT printer_process_irp_write(PRINTER_DEVICE* printer_dev, IRP* irp)
  */
 static UINT printer_process_irp_device_control(PRINTER_DEVICE* printer_dev, IRP* irp)
 {
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(irp);
+
 	Stream_Write_UINT32(irp->output, 0); /* OutputBufferLength */
+
+	WINPR_ASSERT(irp->Complete);
 	return irp->Complete(irp);
 }
 
@@ -533,6 +559,9 @@ static UINT printer_process_irp(PRINTER_DEVICE* printer_dev, IRP* irp)
 {
 	UINT error;
 
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(irp);
+
 	switch (irp->MajorFunction)
 	{
 		case IRP_MJ_CREATE:
@@ -574,6 +603,7 @@ static UINT printer_process_irp(PRINTER_DEVICE* printer_dev, IRP* irp)
 
 		default:
 			irp->IoStatus = STATUS_NOT_SUPPORTED;
+			WINPR_ASSERT(irp->Complete);
 			return irp->Complete(irp);
 	}
 
@@ -584,12 +614,14 @@ static DWORD WINAPI printer_thread_func(LPVOID arg)
 {
 	IRP* irp;
 	PRINTER_DEVICE* printer_dev = (PRINTER_DEVICE*)arg;
-	HANDLE obj[] = { printer_dev->event, printer_dev->stopEvent };
 	UINT error = CHANNEL_RC_OK;
 
+	WINPR_ASSERT(printer_dev);
+
 	while (1)
 	{
-		DWORD rc = WaitForMultipleObjects(2, obj, FALSE, INFINITE);
+		HANDLE obj[] = { printer_dev->event, printer_dev->stopEvent };
+		DWORD rc = WaitForMultipleObjects(ARRAYSIZE(obj), obj, FALSE, INFINITE);
 
 		if (rc == WAIT_FAILED)
 		{
@@ -635,6 +667,10 @@ static DWORD WINAPI printer_thread_func(LPVOID arg)
 static UINT printer_irp_request(DEVICE* device, IRP* irp)
 {
 	PRINTER_DEVICE* printer_dev = (PRINTER_DEVICE*)device;
+
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(irp);
+
 	InterlockedPushEntrySList(printer_dev->pIrpList, &(irp->ItemEntry));
 	SetEvent(printer_dev->event);
 	return CHANNEL_RC_OK;
@@ -644,7 +680,12 @@ static UINT printer_custom_component(DEVICE* device, UINT16 component, UINT16 pa
 {
 	UINT32 eventID;
 	PRINTER_DEVICE* printer_dev = (PRINTER_DEVICE*)device;
+
+	WINPR_ASSERT(printer_dev);
+	WINPR_ASSERT(printer_dev->rdpcontext);
+
 	const rdpSettings* settings = printer_dev->rdpcontext->settings;
+	WINPR_ASSERT(settings);
 
 	if (component != RDPDR_CTYP_PRN)
 		return ERROR_INVALID_DATA;
@@ -826,6 +867,9 @@ static UINT printer_free(DEVICE* device)
 	IRP* irp;
 	PRINTER_DEVICE* printer_dev = (PRINTER_DEVICE*)device;
 	UINT error;
+
+	WINPR_ASSERT(printer_dev);
+
 	SetEvent(printer_dev->stopEvent);
 
 	if (WaitForSingleObject(printer_dev->thread, INFINITE) == WAIT_FAILED)
@@ -842,7 +886,10 @@ static UINT printer_free(DEVICE* device)
 	}
 
 	while ((irp = (IRP*)InterlockedPopEntrySList(printer_dev->pIrpList)) != NULL)
+	{
+		WINPR_ASSERT(irp->Discard);
 		irp->Discard(irp);
+	}
 
 	CloseHandle(printer_dev->thread);
 	CloseHandle(printer_dev->stopEvent);
@@ -850,7 +897,10 @@ static UINT printer_free(DEVICE* device)
 	winpr_aligned_free(printer_dev->pIrpList);
 
 	if (printer_dev->printer)
+	{
+		WINPR_ASSERT(printer_dev->printer->ReleaseRef);
 		printer_dev->printer->ReleaseRef(printer_dev->printer);
+	}
 
 	Stream_Free(printer_dev->device.data, TRUE);
 	free(printer_dev);
@@ -866,6 +916,10 @@ static UINT printer_register(PDEVICE_SERVICE_ENTRY_POINTS pEntryPoints, rdpPrint
 {
 	PRINTER_DEVICE* printer_dev;
 	UINT error = ERROR_INTERNAL_ERROR;
+
+	WINPR_ASSERT(pEntryPoints);
+	WINPR_ASSERT(printer);
+
 	printer_dev = (PRINTER_DEVICE*)calloc(1, sizeof(PRINTER_DEVICE));
 
 	if (!printer_dev)
@@ -930,6 +984,7 @@ static UINT printer_register(PDEVICE_SERVICE_ENTRY_POINTS pEntryPoints, rdpPrint
 		goto error_out;
 	}
 
+	WINPR_ASSERT(printer->AddRef);
 	printer->AddRef(printer);
 	return CHANNEL_RC_OK;
 error_out:
@@ -1016,6 +1071,7 @@ UINT printer_DeviceServiceEntry(PDEVICE_SERVICE_ENTRY_POINTS pEntryPoints)
 
 	if (name && name[0])
 	{
+		WINPR_ASSERT(driver->GetPrinter);
 		rdpPrinter* printer = driver->GetPrinter(driver, name, driver_name);
 
 		if (!printer)
@@ -1025,6 +1081,7 @@ UINT printer_DeviceServiceEntry(PDEVICE_SERVICE_ENTRY_POINTS pEntryPoints)
 			goto fail;
 		}
 
+		WINPR_ASSERT(printer->ReleaseRef);
 		if (!printer_save_default_config(pEntryPoints->rdpcontext->settings, printer))
 		{
 			error = CHANNEL_RC_INITIALIZATION_ERROR;
@@ -1042,6 +1099,7 @@ UINT printer_DeviceServiceEntry(PDEVICE_SERVICE_ENTRY_POINTS pEntryPoints)
 	}
 	else
 	{
+		WINPR_ASSERT(driver->EnumPrinters);
 		rdpPrinter** printers = driver->EnumPrinters(driver);
 		rdpPrinter** current = printers;
 
@@ -1056,13 +1114,17 @@ UINT printer_DeviceServiceEntry(PDEVICE_SERVICE_ENTRY_POINTS pEntryPoints)
 			}
 		}
 
+		WINPR_ASSERT(driver->ReleaseEnumPrinters);
 		driver->ReleaseEnumPrinters(printers);
 	}
 
 fail:
 	free(driver_name);
 	if (driver)
+	{
+		WINPR_ASSERT(driver->ReleaseRef);
 		driver->ReleaseRef(driver);
+	}
 
 	return error;
 }