diff --git a/Makefile b/Makefile
index d3e3138..5887923 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CONFIG_CXX_ALLOCATOR := true
 CONFIG_UBSAN := false
 
 CPPFLAGS := -D_GNU_SOURCE
-SHARED_FLAGS := -O2 -flto -fPIC -fvisibility=hidden -fno-plt -pipe -Wall -Wextra
+SHARED_FLAGS := -O2 -flto -fPIC -fvisibility=hidden -fno-plt -pipe -Wall -Wextra -Wcast-align=strict -Wcast-qual -Wwrite-strings
 CFLAGS := -std=c11 $(SHARED_FLAGS) -Wmissing-prototypes
 CXXFLAGS := -std=c++14 $(SHARED_FLAGS)
 LDFLAGS := -Wl,-z,defs,-z,relro,-z,now,-z,nodlopen,-z,text
diff --git a/malloc.c b/malloc.c
index 0152977..261a044 100644
--- a/malloc.c
+++ b/malloc.c
@@ -296,13 +296,13 @@ static void *slot_pointer(size_t size, void *slab, size_t slot) {
     return (char *)slab + slot * size;
 }
 
-static void write_after_free_check(const char *p, size_t size) {
+static void write_after_free_check(const void *p, size_t size) {
     if (!WRITE_AFTER_FREE_CHECK) {
         return;
     }
 
     for (size_t i = 0; i < size; i += sizeof(u64)) {
-        if (*(u64 *)(p + i)) {
+        if (*(const u64 *)(p + i)) {
             fatal_error("detected write after free");
         }
     }