Index: uspace/lib/c/arch/abs32le/src/stacktrace.c
===================================================================
--- uspace/lib/c/arch/abs32le/src/stacktrace.c	(revision 1bfd3d3b2991b8f2df4cff87d9723059528b9bd1)
+++ uspace/lib/c/arch/abs32le/src/stacktrace.c	(revision 0b4a67a31961a80515a7b28d5b2e27fbb8f7249d)
@@ -56,10 +56,10 @@
 uintptr_t stacktrace_fp_get(void)
 {
-	return NULL;
+	return (uintptr_t) NULL;
 }
 
 uintptr_t stacktrace_pc_get(void)
 {
-	return NULL;
+	return (uintptr_t) NULL;
 }
 
Index: uspace/lib/c/arch/abs32le/src/tls.c
===================================================================
--- uspace/lib/c/arch/abs32le/src/tls.c	(revision 1bfd3d3b2991b8f2df4cff87d9723059528b9bd1)
+++ uspace/lib/c/arch/abs32le/src/tls.c	(revision 0b4a67a31961a80515a7b28d5b2e27fbb8f7249d)
@@ -46,5 +46,5 @@
 uintptr_t __aeabi_read_tp(void)
 {
-	return NULL;
+	return (uintptr_t) NULL;
 }
 
Index: uspace/lib/c/generic/async.c
===================================================================
--- uspace/lib/c/generic/async.c	(revision 1bfd3d3b2991b8f2df4cff87d9723059528b9bd1)
+++ uspace/lib/c/generic/async.c	(revision 0b4a67a31961a80515a7b28d5b2e27fbb8f7249d)
@@ -536,5 +536,5 @@
 		if (callid)
 			ipc_answer_0(callid, ENOMEM);
-		return NULL;
+		return (uintptr_t) NULL;
 	}
 	
@@ -556,5 +556,5 @@
 		if (callid)
 			ipc_answer_0(callid, ENOMEM);
-		return NULL;
+		return (uintptr_t) NULL;
 	}
 	
Index: uspace/lib/c/generic/io/klog.c
===================================================================
--- uspace/lib/c/generic/io/klog.c	(revision 1bfd3d3b2991b8f2df4cff87d9723059528b9bd1)
+++ uspace/lib/c/generic/io/klog.c	(revision 0b4a67a31961a80515a7b28d5b2e27fbb8f7249d)
@@ -52,5 +52,5 @@
 void klog_update(void)
 {
-	(void) __SYSCALL3(SYS_KLOG, 1, NULL, 0);
+	(void) __SYSCALL3(SYS_KLOG, 1, (uintptr_t) NULL, 0);
 }
 
Index: uspace/lib/c/include/unistd.h
===================================================================
--- uspace/lib/c/include/unistd.h	(revision 1bfd3d3b2991b8f2df4cff87d9723059528b9bd1)
+++ uspace/lib/c/include/unistd.h	(revision 0b4a67a31961a80515a7b28d5b2e27fbb8f7249d)
@@ -41,5 +41,5 @@
 
 #ifndef NULL
-	#define NULL  0UL
+	#define NULL	((void *) 0)
 #endif