diff --git a/Makefile b/Makefile
index 671d35b6..39069ac9 100644
--- a/Makefile
+++ b/Makefile
@@ -63,6 +63,7 @@ CFLAGS += -fcallgraph-info=su
 CFLAGS += -g3
 CFLAGS += -I.
 CFLAGS += -std=c99 -Wall -Wextra -pedantic
+CFLAGS += -Wmissing-prototypes
 CFLAGS += -ftrack-macro-expansion=0
 ifdef DEBUG
 CFLAGS += -O0
@@ -354,6 +355,7 @@ summary-diff sizes-diff: $(OBJ) $(CI)
 
 ## Build the test-runner
 .PHONY: test-runner build-test
+test-runner build-test: CFLAGS+=-Wno-missing-prototypes
 ifndef NO_COV
 test-runner build-test: CFLAGS+=--coverage
 endif
@@ -405,6 +407,7 @@ testmarks-diff: $(TEST_CSV)
 
 ## Build the bench-runner
 .PHONY: bench-runner build-bench
+bench-runner build-bench: CFLAGS+=-Wno-missing-prototypes
 ifdef YES_COV
 bench-runner build-bench: CFLAGS+=--coverage
 endif
diff --git a/lfs2.c b/lfs2.c
index 0b02b0ab..d89c42fd 100644
--- a/lfs2.c
+++ b/lfs2.c
@@ -4999,7 +4999,7 @@ static int lfs2_fs_forceconsistency(lfs2_t *lfs2) {
 #endif
 
 #ifndef LFS2_READONLY
-int lfs2_fs_rawmkconsistent(lfs2_t *lfs2) {
+static int lfs2_fs_rawmkconsistent(lfs2_t *lfs2) {
     // lfs2_fs_forceconsistency does most of the work here
     int err = lfs2_fs_forceconsistency(lfs2);
     if (err) {
@@ -5046,7 +5046,7 @@ static lfs2_ssize_t lfs2_fs_rawsize(lfs2_t *lfs2) {
 }
 
 #ifndef LFS2_READONLY
-int lfs2_fs_rawgrow(lfs2_t *lfs2, lfs2_size_t block_count) {
+static int lfs2_fs_rawgrow(lfs2_t *lfs2, lfs2_size_t block_count) {
     // shrinking is not supported
     LFS2_ASSERT(block_count >= lfs2->block_count);