diff --git a/fuzz/fuzzer.h b/fuzz/fuzzer.h
index fddc846..908cda1 100644
--- a/fuzz/fuzzer.h
+++ b/fuzz/fuzzer.h
@@ -22,8 +22,8 @@
  * This file is part of libpsl.
  */
 
-#include <stddef.h> // size_t
-#include <stdint.h> // uint8_t
+#include <stddef.h> /* size_t */
+#include <stdint.h> /* uint8_t */
 
 #ifdef __cplusplus
 extern "C"
diff --git a/fuzz/libpsl_load_dafsa_fuzzer.c b/fuzz/libpsl_load_dafsa_fuzzer.c
index b50d006..41d7757 100644
--- a/fuzz/libpsl_load_dafsa_fuzzer.c
+++ b/fuzz/libpsl_load_dafsa_fuzzer.c
@@ -40,7 +40,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
 	assert(in != NULL);
 
-	// create a valid DAFSA input file
+	/* create a valid DAFSA input file */
 	memcpy(in, ".DAFSA@PSL_0   \n", 16);
 	memcpy(in + 16, data, size);
 
diff --git a/src/psl.c b/src/psl.c
index 351ac00..dc40c73 100644
--- a/src/psl.c
+++ b/src/psl.c
@@ -689,7 +689,7 @@ static int _psl_idna_toASCII(_psl_idna_t *idna _UNUSED, const char *utf8, char *
 		u_strFromUTF8(utf16_src, countof(utf16_src_buf), &utf16_src_length, utf8, -1, &status);
 		if (!U_SUCCESS(status)) goto cleanup; /* UTF-8 to UTF-16 conversion failed */
 
-		if (utf16_src_length >= countof(utf16_src_buf)) {
+		if (utf16_src_length >= (int) countof(utf16_src_buf)) {
 			utf16_src = malloc((utf16_src_length + 1) * sizeof(UChar));
 			if (!utf16_src) goto cleanup;
 
@@ -705,7 +705,7 @@ static int _psl_idna_toASCII(_psl_idna_t *idna _UNUSED, const char *utf8, char *
 		u_strToUTF8(lookupname, sizeof(lookupname_buf), &bytes_written, utf16_dst, utf16_dst_length, &status);
 		if (!U_SUCCESS(status)) goto cleanup; /* UTF-16 to UTF-8 conversion failed */
 
-		if (bytes_written >= sizeof(lookupname_buf)) {
+		if (bytes_written >= (int) sizeof(lookupname_buf)) {
 			lookupname = malloc(bytes_written + 1);
 			if (!lookupname) goto cleanup;
 
@@ -1194,7 +1194,7 @@ psl_ctx_t *psl_load_fp(FILE *fp)
 		if ((m = realloc(psl->dafsa, len)))
 			psl->dafsa = m;
 		else if (!len)
-			psl->dafsa = NULL; // realloc() just free'd psl->dafsa
+			psl->dafsa = NULL; /* realloc() just free'd psl->dafsa */
 
 		psl->dafsa_size = len;
 		psl->utf8 = !!GetUtfMode(psl->dafsa, len);