diff --git a/src/gc/unix/gcenv.unix.cpp b/src/gc/unix/gcenv.unix.cpp
index e7da60747504..bd0c3fd599d4 100644
--- a/src/gc/unix/gcenv.unix.cpp
+++ b/src/gc/unix/gcenv.unix.cpp
@@ -42,6 +42,10 @@
 #include <vm/vm_param.h>
 #endif // HAVE_XSWDEV
 
+#if HAVE_XSW_USAGE
+#include <sys/sysctl.h>
+#endif // HAVE_XSW_USAGE
+
 #ifdef __APPLE__
 #include <mach/vm_types.h>
 #include <mach/vm_param.h>
@@ -49,8 +53,12 @@
 #include <mach/mach_host.h>
 #endif // __APPLE__
 
-#if HAVE_SYSCTL
+#if HAVE_SYSCONF
+// <unistd.h> already included above
+#elif HAVE_SYSCTL
 #include <sys/sysctl.h>
+#else
+#error "Don't know how to get total physical memory on this platform"
 #endif
 
 #ifdef __linux__
diff --git a/src/pal/src/misc/sysinfo.cpp b/src/pal/src/misc/sysinfo.cpp
index 52e8ec065d73..e3574fa23a6c 100644
--- a/src/pal/src/misc/sysinfo.cpp
+++ b/src/pal/src/misc/sysinfo.cpp
@@ -28,12 +28,19 @@ Revision History:
 #define __STDC_FORMAT_MACROS
 #include <inttypes.h>
 #include <sys/types.h>
-#if HAVE_SYSCTL
+
+#if HAVE_SYSCONF
+// <unistd.h> already included above
+#elif HAVE_SYSCTL
 #include <sys/sysctl.h>
-#elif !HAVE_SYSCONF
+#else
 #error Either sysctl or sysconf is required for GetSystemInfo.
 #endif
 
+#if HAVE_SYSCTLBYNAME
+#include <sys/sysctl.h>
+#endif
+
 #if HAVE_SYSINFO
 #include <sys/sysinfo.h>
 #endif