diff --git a/headers/compatibility/gnu/sched.h b/headers/compatibility/gnu/sched.h
index f4b33cfb9f..6a3eead72a 100644
--- a/headers/compatibility/gnu/sched.h
+++ b/headers/compatibility/gnu/sched.h
@@ -32,6 +32,7 @@ typedef __haiku_uint32 cpuset_mask;
 typedef struct _cpuset {
 	cpuset_mask bits[_howmany(CPU_SETSIZE, NCPUSETBITS)];
 } cpuset_t;
+typedef cpuset_t cpu_set_t;
 
 
 #define _CPUSET_BITSINDEX(cpu) ((cpu) / NCPUSETBITS)
@@ -40,12 +41,32 @@ typedef struct _cpuset {
 /* FD_ZERO uses memset */
 #include <string.h>
 
-#define CPUSET_ZERO(set) memset((set), 0, sizeof(cpuset_t))
-#define CPUSET_SET(cpu, set) ((set)->bits[_CPUSET_BITSINDEX(cpu)] |= _CPUSET_BIT(cpu))
-#define CPUSET_CLR(cpu, set) ((set)->bits[_CPUSET_BITSINDEX(cpu)] &= ~_CPUSET_BIT(cpu))
-#define CPUSET_ISSET(cpu, set) ((set)->bits[_CPUSET_BITSINDEX(cpu)] & _CPUSET_BIT(cpu))
-#define CPUSET_COPY(source, target) (*(target) = *(source))
 
+static inline unsigned int
+__cpu_count(cpuset_t *set)
+{
+	unsigned int count = 0;
+	for (unsigned int i = 0; i < _howmany(CPU_SETSIZE, NCPUSETBITS); i++) {
+		cpuset_mask mask = set->bits[i];
+#if __GNUC__ > 2
+		count += __builtin_popcount(mask);
+#else
+		while (mask > 0) {
+			if ((mask & 1) == 1)
+				count++;
+			mask >>= 1;
+		}
+#endif
+	}
+	return count;
+}
+
+#define CPU_ZERO(set) memset((set), 0, sizeof(cpuset_t))
+#define CPU_SET(cpu, set) ((set)->bits[_CPUSET_BITSINDEX(cpu)] |= _CPUSET_BIT(cpu))
+#define CPU_CLR(cpu, set) ((set)->bits[_CPUSET_BITSINDEX(cpu)] &= ~_CPUSET_BIT(cpu))
+#define CPU_ISSET(cpu, set) ((set)->bits[_CPUSET_BITSINDEX(cpu)] & _CPUSET_BIT(cpu))
+#define CPU_COPY(source, target) (*(target) = *(source))
+#define CPU_COUNT(set)	__cpu_count(set)
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/tests/libs/gnu/Jamfile b/src/tests/libs/gnu/Jamfile
index f0f2070022..233e457575 100644
--- a/src/tests/libs/gnu/Jamfile
+++ b/src/tests/libs/gnu/Jamfile
@@ -1,7 +1,7 @@
 SubDir HAIKU_TOP src tests libs gnu ;
 
 UseHeaders [ FDirName $(HAIKU_TOP) headers compatibility gnu ] : true ;
-SubDirC++Flags [ FDefines _GNU_SOURCE=1 ] ;
+SubDirC++Flags [ FDefines _DEFAULT_SOURCE=1 ] ;
 
 SimpleTest sched_getcpu_test : sched_getcpu_test.cpp : libgnu.so ;
 SimpleTest sched_affinity_test : sched_affinity_test.cpp : libgnu.so ;
diff --git a/src/tests/libs/gnu/sched_affinity_test.cpp b/src/tests/libs/gnu/sched_affinity_test.cpp
index a0b58e5d3c..3723de6dd8 100644
--- a/src/tests/libs/gnu/sched_affinity_test.cpp
+++ b/src/tests/libs/gnu/sched_affinity_test.cpp
@@ -8,6 +8,7 @@
 #include <sched.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 
 int
@@ -19,8 +20,12 @@ main(int argc, char** argv)
 		printf("with affinity on CPU 1\n");
 		pthread_t thread = pthread_self();
 		cpuset_t cpuset;
-		CPUSET_ZERO(&cpuset);
-		CPUSET_SET(1, &cpuset);
+		CPU_ZERO(&cpuset);
+		CPU_SET(1, &cpuset);
+		if (CPU_COUNT(&cpuset) != 1) {
+			fprintf(stderr, "CPU_COUNT failed\n");
+			exit(1);
+		}
 		if (pthread_setaffinity_np(thread, sizeof(cpuset_t), &cpuset) != 0) {
 			fprintf(stderr, "pthread_setaffinity_np failed\n");
 			exit(1);
@@ -29,7 +34,7 @@ main(int argc, char** argv)
 			fprintf(stderr, "pthread_getaffinity_np failed\n");
 			exit(1);
 		}
-		if (!CPUSET_ISSET(1, &cpuset))
+		if (!CPU_ISSET(1, &cpuset))
 			fprintf(stderr, "affinity not on CPU 1\n");
 		if (sched_getcpu() != 1)
 			fprintf(stderr, "not running on CPU 1\n");