diff --git a/os-posix.c b/os-posix.c
index 4c2a7f0..35486b8 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -83,3 +83,13 @@ since it has not been updated to support POSIX.1-2008:
 #endif
 	}
 }
+
+long
+osnproc(void)
+{
+#ifdef _SC_NPROCESSORS_ONLN
+	return sysconf(_SC_NPROCESSORS_ONLN);
+#else
+	return 1;
+#endif
+}
diff --git a/os.h b/os.h
index 91cae05..3715987 100644
--- a/os.h
+++ b/os.h
@@ -7,3 +7,5 @@ void oschdir(const char *);
 int osmkdirs(struct string *, _Bool);
 /* queries the mtime of a file in nanoseconds since the UNIX epoch */
 int64_t osmtime(const char *);
+/* queries the number of online processors */
+long osnproc(void);
diff --git a/samu.c b/samu.c
index 05f5597..0c389bc 100644
--- a/samu.c
+++ b/samu.c
@@ -200,8 +200,7 @@ main(int argc, char *argv[])
 	} ARGEND
 argdone:
 	if (!buildopts.maxjobs) {
-#ifdef _SC_NPROCESSORS_ONLN
-		long nproc = sysconf(_SC_NPROCESSORS_ONLN);
+		long nproc = osnproc();
 		switch (nproc) {
 		case -1: case 0: case 1:
 			buildopts.maxjobs = 2;
@@ -213,9 +212,6 @@ main(int argc, char *argv[])
 			buildopts.maxjobs = nproc + 2;
 			break;
 		}
-#else
-		buildopts.maxjobs = 2;
-#endif
 	}
 
 	buildopts.statusfmt = getenv("NINJA_STATUS");