diff --git a/util/FIFO.h b/util/FIFO.h
index b9850a1..ee1abf8 100644
--- a/util/FIFO.h
+++ b/util/FIFO.h
@@ -43,7 +43,7 @@ inline void fifo_flush(FIFOBuffer *f) {
   f->head = f->tail;
 }
 
-inline bool fifo_isempty_locked(const FIFOBuffer *f) {
+static inline bool fifo_isempty_locked(const FIFOBuffer *f) {
   bool result;
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
     result = fifo_isempty(f);
@@ -51,7 +51,7 @@ inline bool fifo_isempty_locked(const FIFOBuffer *f) {
   return result;
 }
 
-inline bool fifo_isfull_locked(const FIFOBuffer *f) {
+static inline bool fifo_isfull_locked(const FIFOBuffer *f) {
   bool result;
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
     result = fifo_isfull(f);
@@ -59,13 +59,13 @@ inline bool fifo_isfull_locked(const FIFOBuffer *f) {
   return result;
 }
 
-inline void fifo_push_locked(FIFOBuffer *f, unsigned char c) {
+static inline void fifo_push_locked(FIFOBuffer *f, unsigned char c) {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
     fifo_push(f, c);
   }
 }
 
-inline unsigned char fifo_pop_locked(FIFOBuffer *f) {
+static inline unsigned char fifo_pop_locked(FIFOBuffer *f) {
   unsigned char c;
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
     c = fifo_pop(f);
@@ -82,4 +82,4 @@ inline size_t fifo_len(FIFOBuffer *f) {
   return f->end - f->begin;
 }
 
-#endif
\ No newline at end of file
+#endif
diff --git a/util/time.h b/util/time.h
index eb79970..ca5059a 100644
--- a/util/time.h
+++ b/util/time.h
@@ -12,7 +12,7 @@ typedef int32_t mtime_t;
 
 volatile ticks_t _clock;
 
-inline ticks_t timer_clock(void) {
+static inline ticks_t timer_clock(void) {
     ticks_t result;
 
     ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
@@ -31,7 +31,7 @@ inline void cpu_relax(void) {
     // Do nothing!
 }
 
-inline void delay_ms(unsigned long ms) {
+static inline void delay_ms(unsigned long ms) {
     ticks_t start = timer_clock();
     unsigned long n_ticks = ms_to_ticks(ms);
     while (timer_clock() - start < n_ticks) {
@@ -40,4 +40,4 @@ inline void delay_ms(unsigned long ms) {
 }
 
 
-#endif
\ No newline at end of file
+#endif