diff --git a/include/fwrite_le.h b/include/fwrite_le.h
index 76127a3..6eb6fd1 100644
--- a/include/fwrite_le.h
+++ b/include/fwrite_le.h
@@ -18,7 +18,11 @@
 #define ifeq_b32_ret(lhs, rhs, value) if (!memcmp(lhs, rhs, 4)) return value;
 
 int detect_endianness(void);
-size_t fwrite_le(void* ptr, size_t size, size_t count, FILE* stream);
+size_t fwrite_le(
+#if FWRITE_LE_NO_MODIFICATION
+	const
+#endif
+	void* ptr, size_t size, size_t count, FILE* stream);
 void reorder_le_be(
 #if FWRITE_LE_NO_MODIFICATION
 	uint8_t* dest, uint8_t* src,
diff --git a/src/fwrite_le.c b/src/fwrite_le.c
index 473124c..e9beb3f 100644
--- a/src/fwrite_le.c
+++ b/src/fwrite_le.c
@@ -37,7 +37,11 @@ void reorder_le_be(
 	}
 }
 
-size_t fwrite_le(void* ptr, size_t size, size_t count, FILE* stream) {
+size_t fwrite_le(
+#if FWRITE_LE_NO_MODIFICATION
+	const
+#endif
+	void* ptr, size_t size, size_t count, FILE* stream) {
 	/*
 	 * warning: this function modifies `void* ptr` by default!
 	 *          (if FWRITE_LE_NO_MODIFICATION in the header is 0)