diff --git a/builtin/grep.c b/builtin/grep.c
index 88b0c80137..3ddfae4e79 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -74,14 +74,32 @@ static int all_work_added;
 /* This lock protects all the variables above. */
 static pthread_mutex_t grep_mutex;
 
+static inline void grep_lock(void)
+{
+	if (use_threads)
+		pthread_mutex_lock(&grep_mutex);
+}
+
+static inline void grep_unlock(void)
+{
+	if (use_threads)
+		pthread_mutex_unlock(&grep_mutex);
+}
+
 /* Used to serialize calls to read_sha1_file. */
 static pthread_mutex_t read_sha1_mutex;
 
-#define WHEN_THREADED(x) do { if (use_threads) (x); } while (0)
-#define grep_lock() WHEN_THREADED(pthread_mutex_lock(&grep_mutex))
-#define grep_unlock() WHEN_THREADED(pthread_mutex_unlock(&grep_mutex))
-#define read_sha1_lock() WHEN_THREADED(pthread_mutex_lock(&read_sha1_mutex))
-#define read_sha1_unlock() WHEN_THREADED(pthread_mutex_unlock(&read_sha1_mutex))
+static inline void read_sha1_lock(void)
+{
+	if (use_threads)
+		pthread_mutex_lock(&read_sha1_mutex);
+}
+
+static inline void read_sha1_unlock(void)
+{
+	if (use_threads)
+		pthread_mutex_unlock(&read_sha1_mutex);
+}
 
 /* Signalled when a new work_item is added to todo. */
 static pthread_cond_t cond_add;